These are generator quick twisting Bottle Caps, made of plastic material, which are safe and durable and can be used with confidence. It is suitable for all kinds of DIY generators, and can be directly screwed to carbonated beverage bottles for use without air leakage, which can bring you a good experience. Features -Color:Light Brown -Material:ABS -Size:3.30X3.30X3.00cm/1.30X1.30X1.18in - Owning the and break resistance ability, very practical, with excellent texture. - Characteristic and with 2 types. Simple and generous , smooth in lines. - Easy to use. Just screw the bottle on the drink bottle. Easy and sealed without letting the air out easily. - For people who love DIY setup, the bottle caps are helper when they are doing the process of generating - Please check whether the sealing ring is firm before use to avoid air leakage. Easy to assemble and mount, will not consume too much time and effort. Package list: 16 x Bottle Caps