After blowing out 3 o-rings during the last brew session (no they weren't on the say fitting either), I want to look into cheaper replacement parts. I measured one I have from B3 and it looks like it is 16mm ID by 19mm OD. I was thinking about going with silicone for slickness and durability sake and found McMasterCarr part number 5233T43. http://www.mcmaster.com/#5233t43/=arkln3
At $13.13 (plus crazy shipping) for 50, it should last a really long time. Does anyone have any other thoughts on the matter?