Question 1

How do I measure my watch crystal size?

Accepted Answer

Measure the outer diameter of the old crystal with digital calipers, or measure the inner seat of the case if the crystal is gone. Crystals are sold by millimeter, typically in 0.5mm increments from roughly 15mm to 41mm. Round to the nearest listed size; a press-fit crystal should match within about 0.1mm, while gasket-set crystals allow slightly more play. Note thickness separately, since most run 1.0mm to 3.0mm.

Question 2

What's the difference between acrylic, mineral, and sapphire crystals?

Accepted Answer

Acrylic (Hesalite/plexi) is plastic — soft, shatter-resistant, and polishable, but scratches easily; ideal for vintage and dress watches. Mineral glass is harder and clearer, a low-cost durable middle ground. Sapphire is the hardest at 9 on the Mohs scale, nearly scratch-proof and best for daily wear or mods, but it's pricier and can chip on sharp impact. Match the material to how the watch gets used.

Question 3

What do flat, domed, and box crystal mean?

Accepted Answer

These describe the profile. Flat crystals sit level for a modern, clear look. Single- and double-domed crystals curve upward, softening reflections and giving the vintage character common on acrylic. Box (or armored) crystals have steep vertical sides with a flat or slightly domed top, a retro skin-diver style. Always confirm the case clears the dome and that the crystal won't touch the hands.

Question 4

How much do replacement watch crystals cost?

Accepted Answer

As a loose part, acrylic crystals typically run $5-$20, mineral glass $8-$25, and sapphire $15-$60 or more depending on diameter, dome, and coatings. Double-domed sapphire with anti-reflective coating sits at the top of that range, and specialty modding crystals for popular Seiko calibers can cost more. These are part-only prices; professional fitting with labor runs higher.

Question 5

Can I replace an acrylic crystal with sapphire?

Accepted Answer

Sometimes, but not always. A mineral glass crystal can usually be swapped for a same-size sapphire. Acrylic is trickier because domed acrylic crystals have a thin rim and tall curve that flat glass can't replicate, so an exact sapphire match may not exist for the case. Check that diameter, thickness, and profile all match, and confirm whether the crystal is press-fit or gasket-set before ordering.

Question 6

Do I need anti-reflective coating on a watch crystal?

Accepted Answer

AR coating cuts glare and improves dial legibility, and it's a popular upgrade on sapphire mod crystals. Listings note whether the coating is inside, outside, or both; inside-only coatings resist wear better since they're protected from contact. Blue-tinted AR is the most common look, and it adds a few dollars to the price. For acrylic crystals, AR coating isn't typical.

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