Crystal glass is low-iron glass characterized by high light transmission and exceptional clarity. It is high-quality, multifunctional glass, and its clarity is typically 25% higher than ordinary glass. This ultra-clear glass is considered the "Prince of Crystal" in the glass family. For these reasons, this product was chosen by Dymax for use in our GS aquarium series. Replacement glass for DYDMTANK45 aquarium measuring 45 cm × 27 cm × 30 cm (5 mm)