Park Tool IR-1. Take the guesswork out of installing cables, wires, and housing inside the frame, IR-1 speeds the internal frame routing of electric wires, shift cable/housing, brake cable/housing, and hydraulic tubing on carbon fiber, Ti, and aluminum frames.
Kit includes three plastic coated 250cm cables with attached magnets and unique fittings, plus an external guide magnet to speed operation
Opposite polarity magnets on cables seek and attach inside frame tubes, making it easy to route through frame entrances and exits. Works with any size frame including tandems