Good sealing per compatiblemance, no air leakage when connected with the cylinder, more convenient to use. Mainly used compatible the thread adapter of the machine cylinder, and can also be used as the air source switch. Made of high-quality materials, high hardness, and wear-, long service life. The thread is tight, superb technology, stable per compatiblemance, and the installation and use 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 colour Differences, Which Does Not Affect Use Colour:Photo colour 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 colour of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.