This used canister muffler fits a Mac Performance 4 into 1 collector exhaust  for a Honda CB500K or 550K, 1971-78. Inside diameter is 2.25" or 57mm at clamping end and it comes with the clamp, however there is no hanger hardware.  I have include 2 photos showing the muffler installed with Mac Performance collector pipes.

 Please note* If you don't have the Mac Performance 4 into 1 collector, the muffler or collector pipe may need modification to fit.  Hanger hardware not included.