Sizing a mineral crystal

[LittleWatchShop]

I have a Fossil watch that belongs to my daughter in law.  It needs a new crystal. 

The crystal has been removed but is in many pieces so I cannot measure it directly.  I can only measure the case.  This is not the first mineral crystal I have replace, but it will only by my second!!

Here are my measurements:

The diameter of the metal case at the top opening:   22.28mm
The diameter of the white neoprene ring recessed inside the case: 21.42mm

My guess is 22mm.  But I am thinking about buying 0.1mm increments above and below this number.

The crystal has straight sides (tiny bevel at the top for looks.

The previous watch where I replaced the crystal, I was able to get the old one out mostly intact, so I could measure it.  Not so this time.

[jdm]

1 hour ago, LittleWatchShop said:

The diameter of the white neoprene ring recessed inside the case: 21.42mm

Nylon gasket. Neoprene is that soft stuff used for wetsuits and the like.

Quote

My guess is 22mm.  But I am thinking about buying 0.1mm increments above and below this number.

22mm won't fit into 21.4.  Fashion and cheap watches always use crystals in the common increment of 0.5mm, what you need is a 21.5mm crystal for a perfect fit.