Good sealing performance, no air leakage when connected with the cylinder, more convenient to use. Mainly used for the thread adapter of the machine cylinder, and can also be used as the air source switch. Made of high-quality materials, high hardness, wear-resistant, long service life. The thread is tight, advanced technology, stable performance, and installation is simple. If you want to use a steam TR21-4 bottle instead of a Quooker Cube bottle, you can use this adapter. Threads: Tr21-4 female to Tr12-3 male. Tips: The product may be updated constantly; due to different batches, the actual product may have slight differences or color variations, which do not affect use. Color: As shown in photo Material: Copper Package Contents: 1 x CO2 Gas Converter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to vary slightly from the real thing. The measurement allowed error is +/- 1-3 cm.