Description : Glass CO2 diffuser , durable as well as elegant , adding a beautiful scenery to your aquarium . This item will dissolve Carbon Dioxide ( CO2 ) speedily into your aquarium or tank . High efficiency of diffusing carbon dioxide . Easily to install and use . Helps to ensure plants receive proper amounts of CO2 , improve the growth and health of your plants with sufficient CO2 supply . Suitable for use as a decoration or provides a good source of aeration for the tank or aquarium . Specification : Material : Glass 20 gallons - Round Size : Approx . 7x5x2 . 5cm / 2 . 76x1 . 97x0 . 98in 28 gallons - Round Size : Approx . 7x4 . 5x2 . 5cm / 2 . 76x1 . 77x0 . 98in 28 gallons - 3 spins Size : Approx . 12 . 5x8 . 5x3 . 5cm / 4 . 92x3 . 35x1 . 38in 28 gallons - 5 spins Size : Approx . 12 . 5x8 . 5x3 . 5cm / 4 . 92x3 . 35x1 . 38in 28 gallons - 8 spins Size : Approx . 12 . 5x8 . 5x3 . 5cm / 4 . 92x3 . 35x1 . 38in Package Includes : 1 Piece CO2 Diffuser 2 Piece Suction Cups Note : To avoid breakage when removing tubing , do not pull tubing off of glassware . Instead , cut tubing carefully along the attachment length to release the glassware . Mount your diffuser using the suction cup ( s ). It should be positioned low in the aquarium . When removing or repositioning the diffuser , pull by the suction cup ( s ) rather than the glass to avoid breakage .