I put RT Gold Valves in my '00 YZ250 this weekend - learned a lot. Anyway, my kit included "Cylinder Seals" they discs the same diameter as the rebound cylinder and have o-rings on the inside and outside. What is it's function, does it help/hurt? They were a PIA to install and a bigger PIA to get back out (without tearing/stretching the outer o-ring) when I found I made a mistake I had to correct. I left the midvalve alone (did not convert to a check plate) and in retrospect I wished I had not installed these seals.
John
John