Need to place some of the remaining air in one cylinder into another? Now both of you can go back in the water together, great item for instructional use when you still need to get some skill completed and someone got low on air. Equalize pressure between two scuba tanks with this 34" yoking device. Complete with hose, two yokes and integrated bleeder units made of chrome plated marine brass for durability and long life. For E-air not for oxygen