384 New Ladies Mineral Watch Crystals. This is a new set of 384 ladies flat mineral watch crystals in 32 different sizes. Each flat natural mineral watch crystal is 1 mm thick. You receive twelve of each size: 18, 18.25, 18.5, 18.75, 19, 19.25, 19.5, 19.75, 20, 20.25, 20.5, 20.75, 21, 21.25, 21.5, 21.75, 22, 22.25, 22.5, 22.75, 23, 23.25, 23.5, 23.75, 24, 24.25, 24.5, 24.75, 25, 25.25, 25.5, and 25.75 mm.