This latest incarnation of Castelli's venerable Free Aero Race bib short design uses the core patterns from it's predecessor for exact fit, however all materials and seat pad have been upgraded. The Free Aero Race 4 features an upper constructed from two pieces of Stripe Mesh fabric. The almost see-through material is slightly ribbed for ventilation and breathability. The finished seams on the straps are comfortable against your shoulders and clavicle. The outer saddle panels for the short use Castelli's Vortex dimpled fabric on legs for compression and aero performance. Forza panels on the inside saddle panels offer non-friction and high compression-based performance. The Giro 4 leg gripper has a contemporary lie-flat raw-cut edge with vertical silicone stripes to keep the short in place without restricting stretch.

The Progetto X2 Seamless seat pad is broken into three parts. The top sheet or skin care layer, the seamless cushion layer which resides below and the viscous comfort inserts. The skin care layer has a four-way stretch, micro denier and bacteriostatic fabric which adapts to the shape of your body and saddle without any folds in the fabric. The seamless layer underneath features multi-density foam with infinitely variable thickness. The pad has been shortened up from previous versions with more padding concentrated in the sit bone areas. At the very high points (sit bone area) the seat pad measures 17mm. These high points are also gel-like viscous areas for total comfort. From there the seat pad tapers to almost no padding in areas where you simply do not need it. This results in a low-volume seatpad that serves up plenty of comfort.