These CO2 bottle caps are incredibly easy to install, making them a convenient choice for both beginners and experienced aquarium hobbyists. Simply twist the cap onto your CO2 generator bottle, and you're ready to go. The user-friendly design ensures a tight fit, preventing any leaks and maintaining optimal CO2 levels in your aquarium. Features -Color:Beige -Material:Plastic -Size:4.00X3.80X3.80 cm/1.57X1.49X1.49in -Note: bottle cap inner diameter: 28 mm; the specification of the trachea that can be connected with the joint is 4 MM in diameter -Secure tightening: quick tightening design ensures a , preventing co2 leakage and maintaining gas purity -Versatile fit: precision manufacturing allows compatibility with various standard co2 cylinder interfaces -High pressure stability: made from high pressure resistant materials, ensuring the stability of the cap and bottle -Easy portability: compact and lightweight, ideal for outdoor activities like barbecues and camping -Prolonged co2 storage: efficient sealing technology minimizes gas loss, extending the co2 usage time inside the bottle for long term storage Package list: 3 x reactor caps