This set contains three sheet of 5/16 x 5 x 12 dead flat float glass and 7 sheets of 3M lapping film 4-1/4 x 11 in the following microns sizes .3. 1,3,5,12,30 and 40 5/16 Float glass is dead flat and the perfect substrate to attach abrasive sheets Float glass will accommodate a half sheet of lapping film