45/42/38MM Exhaust (Step) Adjuster Pipe. These little friends help you to fit a muffler on a modern exhaust. Also available in multiple sizes. 

This one:  45/42/38MM
This is the outer diameter
The material has a thickness of 1.5MM

So, a 45/42/38mm pipe has a 42/39/35MM inner diameter.

Price PER 1 piece