1----5mm crystal clear low iron optical glass, >91% Clarity. 2---Tank Dimensions: 7.9" L × 7.9" W × 7.9" H (20cm x 20cm x 20cm). 3---Capacity: 2.1 Gal. 4---The 45° mitered edges are bonded together using high performance German silicone specifically designed for aquarium construction. 5---Premium quality, invisible glue joints for perfect viewing.