- Easy to use: simply screw the cap onto a standard beverage bottle to create a tight seal that prevents air from escaping. - Rust-free plastic: made from plastic that resists rust and is safe around fish and aquarium life. - Supports CO2 delivery: if the water weed in your aquarium grows slowly and needs more CO2, this bottle cap helps provide it. - Wide compatibility: the CO2 bottle cap is suitable for most DIY reactors. - Reliable performance: delivers a secure, leak-minimizing connection for consistent CO2 delivery. Example applications - Set up a budget-friendly CO2 system for a small planted freshwater aquarium using a DIY reactor and a standard bottle reservoir. - Replace a worn or leaking cap in an existing DIY CO2 setup to restore a tight seal. - Use as a practical upgrade for hobbyists building or maintaining a CO2 system that requires a reliable bottle cap.