I have an old Sterling Bronze and a seal went. I measured the three seals and got them to be 12.5mm 17 mm and 2.5 thick.I fitted them and the gun does not leak gas.The problem is it's lost all power.so I guessed the seals I fit were the wrong size.when I got it home I gassed it up and the seals are not leaking but previously to the seal change the gun was fine.