CageMount was made by Topeak for attaching an additional water bottle cage to the handlebar or seatpost. We find it is also useful in converting rear rack mount lights to seatpost mount. The CageMount tube clamp can be rotated 90 degrees to find the perfect orientation when clamping to your handlebar, seatpost, or any tube with a 22mm to 38mm diameter - thanks to the adjustable tube clamp.