Thanks! I went and bought 1 inch because that is how deep the hole is. With the gasket and muffler flange I got a good seating to them. Thanks for all your help.
I have a Kohler pro 27 that keeps losing one of the exhaust bolts and my bolt supply is out. What size are they (I looked in the service manual but no luck) and how can I prevent it from falling out, now the second time. I do not want to use the wrong product on the alum head.