Cat. H-12-Collagen: 12 mm diameter, # 1 thickness, 45 pieces of CE certified crystal clear German glass coverslips with rat tail type I collagen coating on both sides for cell culture and confocal fluorescence microscopy, sealed 15 pieces per bag x 3 = 45, sterilized, ready to use. The Cat. number "H" stands for half package = 45 pieces. You can order full package GG-12-collagen = 90 pieces, which is identical products as this H-12-collagen.