The Race knee/shin uses the unique X-fit design that helps keep the guard in place without bunching behind the knee. The top of the vented neoprene liner is built to be as slim as possible to prevent catching on the shorts. The hard caps have vent holes and the EVA foam is vented to create a tough, yet ventilated knee/shin guard.
Man, these rock. I don't really notice them cranking around, but when you have to get off the bike at speed you can just hockey-goalie-slide on these suckers, over rocks and broken glass and rebar, and get right up and go riding. Had a good get-off at a downhill event, skidded over large rocks and into a tree leading with these guards - felt like a pillow fight. For the dough, they save your knees and legs really effectively and inexpensively. Cannot recommend enough.