Do I need to add bolt and nut to this clamp, or are they already attached?

Bolt and nut are included with the clamp. You'll receive the complete assembly ready to install.

Can I use this clamp if my exhaust pipe is slightly smaller than 2.75"?

This clamp is sized for 2.75" piping. Using it on undersized tubing will create gaps and poor clamping pressure — not recommended. Verify your exhaust diameter before ordering.

Will this clamp work on a custom or aftermarket exhaust system?

Yes, as long as your piping measures 2.75" in diameter. The clamp works on any exhaust tubing that matches that size, regardless of system brand or configuration.