Soda CO2 Gas Converter Adapter for TR21-4 Female to TR21-3 Male Thread. Good sealing performance, no air leakage when connected with the cylinder, more convenient to use. Mainly used as a thread adapter for soda machine cylinders and can also be used as an air source switch. Made of high-quality materials, high hardness, wear-resistant, and long service life. The thread is tight, with superb craftsmanship and stable performance; installation and use are simple. If you want to use a Sodastream TR21-4 soda bottle instead of a Quooker Cube bottle, this adapter can be used. Threads: TR21-4 female to TR21-3 male. 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 includes: 1 x Soda CO2 Gas Converter. Only the above package content is included; other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to differ slightly from the real thing. Measurement allowed error is +/- 1-3 cm.