Didn’t recall saying changing them was difficult, just in my experience not every seal is perfect with the nylons. This particular device threads into the center of the nipple from the CO2 tankThis is a mainly UK site and this device appears to originate from a non uk Amazon site. changing o rings is hardly an onerous task.So where does it fit and what thread is that
Shouldn't use rubber with CO2 as CO2 "dissolves" in rubber. Depending on type of rubber either melts/softens/runs or hardens up and cracks. Should use PTFE/nylon for o-rings/washers around CO2.