How are Happy Trails SL Rack and SU Rack different? The SL Rack is designed to carry soft luggage, while the SU Rack can carry soft or hard luggage of any kind. In construction the SU Rack differs in that the loop tubing is 3/4" square steel as opposed to 5/8" round. But even more important every SU rack has a third mounting point for greater strength. Finally it has a rear bumper which ties both sides together.
If you only want to carry soft luggage, then the SL Rack is for you. If you might want to carry hard luggage at some time, then you need the SU Rack. People use our SU Rack for every kind of hard luggage imaginable. They fix the luggage to the rack using our mounting puck system. Our mount kits make it a cinch to take your panniers on and off.