This Shiftmate is just to improve the cable line into the rear mech, it leads to crisper gear changes. Replaces older items (no longer available) such as Avid Rollamajig, Mr Control Roller (really for V-brakes), Acor Pizza Cutter, Tiso P-Pue and Crud Cog Hog.
Avid Rollamajig Acor Pizza Cutter Crud Cog Hog