TromboneChat

Are trombones supposed to have "zero gap" between the mouthpiece and leadpipe? On my soprano trombone, I measured a gap of 5mm. I found out Harrelson company offers shim kits to address this issue, but don't know if it is worth it. What do you suggest?

The majority of trombones don't have an actual gap at all, because the receiver has a receiver taper that continues into the leadpipe.