A Little Bit About Seiko’s Hardlex Crystal

While Seiko is known for creating an immense variety of high-quality and affordable watches, the brand is famous for its invention of the Hardlex crystal. As many enthusiasts know, Hardlex is Seiko’s patented glass material, which they use to protect the dials of many of their models. Although some people appreciate and admire Hardlex for doing its job, others prefer to replace it with something else. In this article, we will be comparing Seiko’s Hardlex glass with the other kinds of crystals currently present in the market. For those who are sold on this bit of Seiko technology, we will also be providing a list of the best timepieces that use Hardlex crystals in their cases.

Seiko’s Hardlex Crystal

Hardlex is a type of crystal glass Seiko produces by heating a mixture of barium and silicon. According to Seiko, this material comes in several grades and is more scratch-resistant than run-of-the-mill mineral glass. Customers can typically find Hardlex in some of Seiko’s more affordable collections, such as the Seiko 5 series. Depending on the model you choose, the crystal may come with a treatment of AR (anti-reflective) coating.

Hardlex vs. The World of Watch Crystals

closer view of Seiko 5 Sports automatic watch
Image By: WayTru (Flickr)

Just to be clear, none of these materials are minerals dug straight out of the mines. These are crystals synthetically made from compounds and mixtures that are tempered in blistering heat to boost the overall resistances of the material. That said, here are the matchups against Seiko’s Hardlex crystal.

Hardlex vs. Acrylic (Plexiglass)

Acrylic crystal, otherwise known as plexiglass, is probably the weakest material in this category. The product is made from plastic, is cheap to produce, and is very easy to replace. Although you usually see this type of acrylic glass on lower-priced watches from brands like Timex and Lorus, some high-end timepieces, like the Rolex Datejust, can also sport acrylic glass on their cases. In a comparison of the two types of glass, Hardlex easily comes out on top, as the harder and more scratch-resistant material. That said, acrylic has its own strengths. For instance, it is actually easier to buff out the scratches on acrylic glass. In addition, acrylic tends to be more shatterproof than the other types of watch crystals out there.

Hardlex vs. Mineral

Mineral glass is the most common kind of crystal found in entry-level watches. This material is moderately durable and provides a neat and clear lens through which the wearer can view their timepiece. Although Seiko states that their Hardlex crystal is more resistant to scratches than mineral glass, there have not been many demonstrations that prove that claim. In most cases, Hardlex and mineral crystals tend to offer similar results. Both materials have limited resistances and can be polished to remove light scratches.

Hardlex vs. Sapphire

On the Mohs scale of hardness, sapphire crystal measures at a hardness level of 9, just one point below diamond, which is famously hardy and resistant to scratches. Sapphire glass is the most commonly used material for high-end watches. Virtually scratch-proof, sapphire stands above Hardlex as the more capable watch crystal. Though that may be the case for scratch resistance, there are some other things that Hardlex can do better. For one, sapphire glass is quite brittle and can crack or shatter after a tremendous impact. Hardlex crystal, on the other hand, is not as fragile and is less likely to break even after an impressive blow. Another aspect to consider is the price. Since scratch resistance is a crucial factor for watch crystals, sapphire tends to be a lot more expensive than Hardlex due to the pricey tools needed to process it. As a result, replacing a sapphire crystal would cost you a lot more than replacing a Hardlex one. Furthermore, since sapphire is highly reflective, watchmakers typically treat the glass with a layer of AR coating, which adds to its cost. Lastly, in terms of aesthetics, there is actually not much difference between the two watch crystals.

Hardlex vs. Sapphlex

Besides their Hardlex glass, Seiko has also manufactured another trademark crystal known as Sapphlex. Essentially, Sapphlex is a mineral crystal coated in sapphire. By adopting the best qualities of both mineral and sapphire glass, Sapphlex manages to be both scratch-proof and shatter-resistant. On the whole, Sapphlex outshines Hardlex in scratch resistance, quality, and durability. However, it is also a bit more costly to replace.

When to go for Hardlex?


When you’re on a tight budget, going for the more affordable option is a no-brainer. Despite being relatively cheap, Hardlex is still a reliable watch glass that can withstand a good amount of impacts and light scratching. Furthermore, if your Hardlex glass starts garnering too many deep scratches, it won’t be that expensive to replace it either. Seiko also states that their Hardlex crystal is indeed more scratch-resistant than mineral crystals. Indeed, it will not do you any harm to test this claim out for yourself.


While some people use watches to add a little class to their get-up, others need a timepiece to fulfill a specific purpose. If you are looking for an affordable wristwatch that you can bring to various expeditions, picking a model that has a Hardlex glass would be a terrific option. As previously stated, Hardlex is a material that will not shatter easily, which is good for tight spots and bumpy adventures.

Watches That Sport A Hardlex Crystal

1. Seiko Presage Cocktail Time Automatic (SRPF39J1)

front view of Seiko Presage Cocktail Time Automatic Ref. SRPF39J1watch

The Presage collection is one of Seiko’s most recent successes. With the series came this wristwatch — the Seiko Presage Cocktail Time Automatic Ref. SRPF39J1. Worth approximately $500 USD, this automatic timepiece stands as an affordable dress watch with an exquisite and unique aesthetics inspired by a cocktail beverage — the margarita. The watch has a 38.5mm stainless steel case paired with a Milanese mesh bracelet. What truly makes this model stand out is its patterned mocha dial. With its pronounced indices and minimalist look, this mocha dial has an alluring face that is also easily legible to the eyes. The dial is protected by a Hardlex crystal, while the watch itself is powered by Seiko’s Caliber 4R35. The 4R35 is an automatic movement that features manual winding and a 41-hour power reserve. Thanks to the Ref. SRPF39J1’s exhibition-style caseback, wearers can view the 4R35 and its many components at work. 

Overall, the Seiko Presage Cocktail Time Ref. SRPF39J1 is an astounding watch in many aspects, including its price. Of course, its affordability is related to its use of inexpensive but durable Hardlex crystal. Altogether, you really cannot go wrong with an affordable luxury like this.

2. Seiko Mechanical Cocktail Time (SARB065)

front view of Seiko Mechanical Cocktail Time Ref. SARB065 watch

The Cocktail Time is a line of hefty and elegant dress watches inspired by cocktail beverages that showcase incredible Japanese watchmaking techniques. For those who are fond of more sizable watches, have a look at the Seiko Mechanical Cocktail Time Ref. SARB065. The wristwatch measures 40mm in diameter and is 13mm thick. Like most Seiko Cocktail Time models, all the attention goes to the unique dial. Protected by a domed Hardlex crystal, the dial has a blue sunburst surface with pointed hour indices and a date window at 3 o’clock. Because of its reflective surface, the Hardlex glass complements the dial and makes it look even glossier. Powering the watch is the Seiko 6R15d caliber movement. The caliber is an automatic movement with manual winding and hacking capabilities. Sheltered by a see-through caseback, the 6R15d has a power reserve that can last up to 50 hours. 

The SARB065 comes at an affordable price of approximately $480 USD. Without a doubt, this Seiko Mechanical Cocktail Time is a gorgeous watch. Accompanied by a black semi-gloss leather strap, this timepiece highlights the brilliance of Japanese artistry, craftsmanship, heritage, and expertise.

3. Seiko Prospex PADI Diver Samurai (SRPB99K1)

front view of Seiko Prospex PADI Diver Samurai Ref. SRPB99K1 watch

The Seiko Samurai is an iconic watch. It is a timepiece that has received a lot of love and admiration, not only for its marvelous design but also for its top-notch quality and affordable price. Several factors contribute to making the Seiko Samurai so exceptional. Possessing a water resistance rating of up to 200 meters, the Seiko Samurai is fully capable of traversing both shallow and deep waters. 

The Seiko Samurai also comes in a sturdy stainless steel case coupled with a bracelet of the same material. On top of its steel exterior are a Hardlex crystal and a unidirectional rotating bezel which sports the highly recognizable Pepsi colors that watch enthusiasts love. Its black dial features a pleasing wave pattern accompanied by thick, outlined hands and indices for optimal legibility. In addition, Seiko equipped the watch with the LumiBrite technology. LumiBrite is another one of Seiko’s trademarks. Aside from providing ample luminescence in dark environments, LumiBrite is also 100% eco-friendly. Operating the Seiko Samurai’s mechanisms is a 4R35 automatic caliber. This movement features manual hacking and winding capabilities and can last up to 41 hours. 

The Seiko Samurai is everything a sports enthusiast could ever want. It is the perfect timekeeping companion for you to bring to your different adventures. With its impeccable looks, polished exterior, and sturdy Hardlex glass, this honored timepiece can take on all kinds of hardships, just like an actual Samurai. The Seiko Prospex PADI Diver Samurai costs $490 USD and is one of the best affordable divers watches out there.

4. Pulsar Gents Accelerator Solar Chronograph (PX5019X1)

front view of Pulsar Gents Accelerator Solar Chronograph Ref. PX5019X1 watch
Image By: Pulsar Watches

Aside from Seiko watches, Hardlex is also used to protect the dials of Lorus and Pulsar timepieces. One distinguished Pulsar watch that comes to mind is the Pulsar Gents Accelerator PX5019X1. First of all, this watch costs only around $150 USD, which is quite surprising, given its sleek and urban looks. Encased in stainless steel, this wristwatch features a black tachymeter perched on top and is water-resistant up to depths of 10 bars (100 meters). The Pulsar PX6019X1 is also equipped with a pretty intriguing movement. While it is a quartz caliber, the movement is also solar-powered. As a result, its power reserve can last up to an astronomical 4,380 hours — equivalent to 6 months. The dial on top of the movement has a sporty black surface with luminescent hands and indices that provide legibility in the dark. 

If you want a multi-faceted watch that is not as expensive as it looks, then the Pulsar Gents Accelerator PX5019X1 is the timepiece for you. Coupled with its protective Hardlex crystal, this model offers functionality, style, and convenience, all for a very affordable price.

5. Lorus Gents Titanium Watch (RXD425L8)

front view of Lorus Gents Titanium Watch Ref. RXD425L8 watch

As previously mentioned, other brands also equip their watches with Hardlex crystals. For Lorus, they have created a notably affordable and reliable timepiece known as the Gents Titanium Watch RXD425L8. Lorus forged the model with hypoallergenic titanium, allowing wearers with sensitive skin to sport the 35mm RXD425L8 without developing any allergic reactions. Its dial boasts a delightful cream face that has a 24-hour inner chapter ring and a date window at 3 o’clock. Protected by a layer of Hardlex glass, this watch is water-resistant up to depths of 100 meters. Lorus pairs this watch with a military green fabric strap and a reliable quartz movement.

What makes titanium such an astounding material is its ability to replicate the sturdiness of steel while weighing much less. With the addition of a Hardlex crystal, the Lorus Gents Titanium proves to be an acutely sturdy and dependable watch that easily aligns itself with other more mainstream military models. Worth approximately $80 USD, this Lorus timepiece is exceedingly budget-friendly.

6. Seiko 5 Sports (SRPD59K1)

front view of Seiko 5 Sports Ref. SRPD59K1 watch

Seiko 5 Sports is home to a far-reaching variety of sports watches. A distinct model that catches our attention is the SRPD59K1. Retailing at approximately $340 USD, this Seiko 5 Sports timepiece showcases a 42.5mm stainless steel exterior accompanied by a stunning orange dial. Protected by a Hardlex crystal and a unidirectional rotating bezel, the orange dial bears a vibrant aesthetic with geometric indices and thick hands. In the dark, the watch is capable of illuminating itself with Seiko’s LumiBrite technology, offering users a light source to help them read the time efficiently. Below the watch face is a 4R36 movement equipped with a 41-hour power reserve. Sealed by a screwed-down see-through caseback, the Seiko 5 SRPD59K1 possesses a water resistance rating of 100 meters.

As watch fanatics would say, the Seiko 5 SRPD59K1 is not a “true” divers watch, as its water resistance capacity is fairly standard. However, if you want a splendid, good-looking timepiece that you can bring for a swim, then this Seiko model will not disappoint. With its stainless steel case, Hardlex glass, and bright orange dial, this watch is affordable, robust, and eye-catching.

7. Seiko 5 Sports (SRPE65K1)

front view of Seiko 5 Sports Ref. SRPE65K1 watch

Yet another representative from the Seiko 5 Sports collection is the Seiko SRPD65K1, a timepiece with a simple yet handsome black and dark grey design. While the two-tone dial is impressive, to say the least, its hard-coated stainless steel case and bracelet also give the timepiece a PVD-esque look. The SRPD65K1 uses the same automatic movement as the SRPD59K1, listed above. As such, it also has manual hacking and winding capabilities and runs on a power reserve that can last up to 41 hours. The SRPD65K1 bears a water resistance capacity of 100 meters and has LumiBrite technology applied on its hour markers and hands. Sealed off by Hardlex crystals on its front and rear, this Seiko timepiece is approximately worth $400 USD. 

There is no going wrong with selecting a watch from the Seiko 5 Sports line. With its affordability and widely recognized looks, the Seiko SRPD65K1 will surely grab the attention of anyone who sees it. The sleek Hardlex glass embedded on top of it not only provides ample protection but also matches the watch’s overall understated looks.

Final Thoughts

Despite being the go-to watch crystal for lower-priced timepieces, the fact remains that Seiko’s Hardlex is a reliable and sturdy watch glass. While offering wearers a good view of their watch, it can also easily take on a few good hits and some light scratches — making it an excellent and budget-friendly choice.

Looking for a REALLY good divers watch? Have a look at Orient’s Mako II.

Featured Image By: Shane Lin (from Flickr)

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