From Minnesota, PROBLEM SOLVERS's Backstop / Two Cable with Slots that shape our "I wish I had". It can be converted to a 2-cable routing specification simply by clamping the round tube frame. The interior hub can be mounted on a single speed frame that does not have a cable stop for the shifter, and it has all the possibilities.
Designed for the top tube of a round pipe frame. Please note that if you attach it to a frame that does not match the size, you may damage the frame.