You are bidding on domed sapphire crystal.  It is 30mm in diameter with blue AR coating on the flat side.  It fits Seiko watches that require a 30mm crystal. The crystal is also 1.2mm at the edges and 3.5mm at the center.

The watch pictured is just for purposes of showing the crystal.  The watch pictured is not sold as a part of this listing.

Please feel free to message me if you have any questions