hi i have bought a brand new catalytic converter with header pipe from catco and it came with 2 new double sided screw bolts and 2 new nuts as well as a 2 1/2 clamp.

but it also came with a round 2 1/2 inch peice of very very light metal. its hollow in the middle like a donut.. and fits nice and snug in the out pipe of the cat.

is this a peice of welding solder that i put between the catco pipe and my existing pie to weld them together.? and if it is can i use a can butane torch to heat it and weld the 2 pipe'* together.? thanks

No you cant weld it with a butane torch.
Mig/tig or metal arc to weld on exhaust.

ok im glad you warned me on that.. but is that peice i described what it'* for. o weld the 2 pipes together? thanks man..

If you got a cat with the downpipe already attached, then it sounds like a downpipe flange gasket (a crush gasket)...a thin piece of metal that sandwiches inside, between your back manifold and the downpipe to the cat to seal the gap at the pipe and back manifold from leaks, not between the cat and the rest of the exhaust piping going to the back of the car.