Allows the oxy mask to clip or strap on. Comes as shown in the photos. One receiver is missing the backplate (see photos). Check out my other items. The item "Two (2) Scott ATO #345-301 Ox Rec for Pilot's Flight Helmet NSN1660-00-440-5553" is in sale since Sunday, June 14, 2020.This item is in the category "Collectibles\Militaria\1992-2001\Original Period Items". The seller is "rinaspartsstore" and is located in Garden Grove, California. This item can be shipped worldwide.