Exhaust Joint sealer?

What are people using to seal up their exhaust joints?
I've been using some high temp silicone which is rubbish. Just bought some stuff from Holt which apparently expands as it cures. Not sure I want that...
I've been using some high temp silicone which is rubbish. Just bought some stuff from Holt which apparently expands as it cures. Not sure I want that...