Bontrager Seatpost Rack
Bontrager's Seatpost Rack is a great choice for frames without built-in eyelets, this versatile rear rack quickly attaches to your seatpost with an easy to use four-bolt design. Compatibility with Trek's Interchange System means it mates seamlessly with a variety of Interchange bags (sold separately) that install fast and secure. It fits both 27.2mm and 31.6mm seatposts.
Capacity: up to 20 pounds