Cat. H-22-Collagen: 22 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. H-22-collagen is half size package of GG-22-collagen. The collagen coated coverslips are identical in the two cat. numbers.