VIV's hand-blown Glasswares are the most favored in the aquatic world offering an outstanding elegance to any aquarium. Designed with an emphasis on functional beauty, each VIV glass piece is handmade in China by skilled glass workers. The pieces are formed from crystal clear borosilicate glass, the same material used to make high end lab equipment. Japanese glass craftsmen carefully hand finish each VIV part to the highest standards with smooth edges and attention to the smallest details. VIV's Medium CO2 Simple Diffuser is suitable for aquariums up to 20 gallons. The simple design adds a delightful look to any planted aquarium. The design is easy to set up and uses suction cups for mounting, therefore it can be used on any thickness of rim. The diameter for the ceramic disc is 30mm. Important Info: All ceramic discs, tubes, or surfaces MUST soaked in water for at least 30 minutes before use. Always wet the glass tubing before inserting the silicon or rubber tubing to avoid damaging Glassware.