Trek-emonda-seat-cap, trek parts the trek emonda slr 10 seat cap is a special carbon seatpost attachment for the trek emonda slr 10 and sl/slr frames with an integrated seatpost. available in different lengths. setback: 20mm model: black. Oldnslow2 wrote: from everything i see the sl and slr use the same part. "trek offers a choice of two lengths for the seatpost cap (135mm and 175mm) along with two offsets (5mm and 20mm)" if you're still not sure, email trek's customer support ([email protected]).i've had a number of questions and they were quick to respond.