The 10R transmissions make alot of pressure, every bore plug on the factory valvebody is not o ringed which can cause slight pressure loss. What better way to keep fluid pressure within the valvebody by upgrading the bore plugs with o-rings? 
 
Included is one o-ringed bore plug for the primary pressure regulator valve, and one for the Torque Converter control priority bore. You also get some spare O-rings just incase you accidentally tear one on install.