The Fox Racing Baseframe Pro is a mesh baselayer that carries back and shoulder protection under a jersey on rough terrain. D3O inserts sit at the back and shoulders, and body heat softens the foam until it conforms to the rider's shape. The low-profile layout keeps the protection close to the body instead of adding a separate pad over clothing. What Our Gearhead(R) Experts Are Saying:"I wear the Baseframe Pro on long pedal days because the back foam is perforated, so air reaches my back through the insert. The grooves in that foam let it flex as I hinge over the bars on climbs."