DR Gizmo on 520 ?
 

Does anyone recognize the part that is on the DR cable loop going on the pic of the LX DR on 520 (from Trek's website)?

I have a 32T freewheel on a roadbike using 105 DR and it works fine with just some attention to the length of the loop. Even so, the stop on bike's dropout is useless (i.e., the the DR is back too far for the screw to make contact). It looks like the gizmo is designed to address that. Thanks :)

That's just a boot/cover to keep dirt out. Nothing more, nothing less.