This JK USA 7D feels a tiny bit smaller in diameter than the current Bach 7D, but this doesn't bother me. The throat entrance is tighter on the JK, and the rim is more comfortable. The JK's backbore feels more open than the Bach's #76 backbore. (This, alone, is a big improvement.) The JK 7D, for me, is easier to play, and it doesn't hurt like the Bach does when playing above high C. The JK is brighter, but its upper register is fuller because of the slightly larger backbore.