o-ring size for mixing manifold
 

Anyone know the size of this o-ring? I thought I had one in my gasket kit, but it didn't seem to work (too fat). I tried one I had laying around that was smaller that seemed to work for a while, but now it is leaking a little.

This is for the metal tube that diverts water to the heater core.

EDIT: Here is the part O-RING (E301-15-287) http://parts.arlingtonmazda.com/prod...52d287%29.html fyi it's called a bypass oring