The Cateye RM-2 bracket mounts directly to the rails of your saddle, providing a secure platform to mount your light to while leaving your seatpost free. A good option for second lights or for cyclists running dropper seatposts, or bikes with minimal seatpost exposed. This bracket is only compatible with the Volt 50 light. The Cateye RM-1 saddle rail mount fits a wider range of lights.