The stock Yokomo o-rings (BD-500G0) that came in my kit was a bit tight. I read on this thread that the Kyosho o-rings (ORG05) were also on the tight side. I opt'd to go with the new Yokomo o-rings (BD-500G0B) which was noticeable more free compared to the stock piece. I haven't run my car yet so I wasn't sure if they would eventually leak. It's good to know that they work.
5tylez - Thanks for sharing the info from Corey. I had the pleasure of watching the man do work in the past couple of big races. The car Corey puts down for Andrew is always dialed! I hope that they can obtain the results that they are seeking at the IFMAR Worlds.