Most of the baffles I have seen use a single bolt. I put the hole at the bottom slightly to the inside where it won't be seen.

The 4" baffles I posted I used to use in 1 3/4 drag pipes for some back pressure and it doesn't effect sound at all. Make sure when ordering any baffles you measure the dia. where you want them to go and be sure to get the right size.

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