Fingers crossed it'll cut ally

[Jonathan]

I bought a set of o-rings but because they are round and the rubbers fairley hard you dont get enough surface area for the vaccum, it tends to role across the rubber, my larger rubber ring is flat and compresses under the force, the o-rings dont :(

You could try neoprene?

neoprene sheet | eBay

I can send you a bit if you want to try it...