CGA870 to Female Din – Straight Handle This is an adapter that is used for filling purposes. This adapter is female din (just like a scuba tank) you can hook this up to your din whips and fill medical oxygen bottles. Johns Tip’s: Where is the O-ring Ok you all, this is not scuba so there is no o-ring. We have a fancy item here called a bodock seal. Now if you want to sound important to your buddies throw that at them next time. The Bodock seal actually hooks to the center pin assembly and does the sealing.