I decided to change the o rings in my gas cylinder adaptors The ones that go on those cheap non threaded to make them be used on tbreaded. I am sorry I have temp forgotten the names, having a ' senior moment' lol. I have a stock of o rings but not this small ( see pics). Can anyone give me the sizing please? I have a lot of these cylinders to use up as some have got a bit corroded. Not dangerous but need using.