Cat. GG-22-Collagen: 22 mm round shape, # 1 thickness, 90 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 6 = 90, sterilized, ready to use. GG-22-1.5-collagen if a better choice if confocal imaging is required after cell culture.