Brass material: thread. The adapter is made of brass, with good and wear resistance, which ensures the durability and airtightness of the connection, suitable for long-term use. Easy installation: cylinder converts adapter, when you connect the gas bottle, first align the threaded connection, then tighten it by hand, then tighten it moderately with a wrench, do not use too much force so as not to damage the sealing ring of the thread load. After tightening, slowly open the gas source and check if there is a leakage to that the adapter can be used normally. Working pressure range: cylinder thread converts adapter, working pressure can be lower than 3000 psi (. 207 bar), much higher than the normal working pressure of 100-120psi for home soda machines, within the safe range of high pressure gas can be effectively controlled to that the inflation process is safe and stable. Thread size: 1 x thread conversion adapter (TR21-4 female to TR21-3 male). Flexibility when using TR21-4 threaded bottles in Quooker Cube system, please check the size before purchasing. Wide Application: CO2 brass cylinder adapter suitable for most TR2 standard CO2 bottles on the market (need to confirm the thread type of bottle), it is an ideal accessory for Quooker Cube users. The compact size is also suitable for use in outdoor activities. Color:Yellow & Red Material:Metal Package Contents: 1 * connector with cap 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.