So I am getting small leaking from the atmosphere vent hole. The only thing I can think of is the o ring inside where the reg sit. Or could it be another different cause? Well anyway I took the o ring inside where the reg sit out and compare it to all the o rings I have and none fit. They were either too small or too big. Does anyone know what size the o ring is? I look at the part diagram and can not tell which it is. Can anyone tell me what part that is on the diagram?