Mouthpiece Gap on Soprano Trombone

[davidicharp]

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?

[Doug Elliott]

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