Cat. H-18-Collagen: 18 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, sealed 15 pieces per bag x 3 = 45, sterilized, ready to use, can be used with 12 well plates, GG-18-collagen is identical to this H-18-collagen except packing size to be 90 pieces.