Little delrin like ring that goes into feedneck as as spacer like.
Top screw and lever are for tightening/loosening grip on hopper neck. Bottom screw is what holds it in place so it doens't move up/down/left/right.
My Marq 6 and Vlocity. Completely stock raceway. Not cut/sanded. Is the tallest possible.
I can try and get better pics of the second if needed. If not I hope this helps.