Designers at Castelli took things seriously when they teamed up with Team Sky to engineer the Free Aero Race 4 Limited Edition Bib Shorts. This meant taking trips all over France, England, and Belgium to gather every bit of feedback possible to fine-tune these race-ready bibs. The result: a feather-light aerodynamic bib that combines Castilli's Vortex dimpled fabric to slice through the wind and gain every second of free speed you can, paired with Forza fabric that stretches gently around your muscles for a next to skin fit. While you may be familiar with the Free Aero Race 4 from previous years, the 2019 sees a few upgrades above years past -- like a new leg gripper that pairs with the lie-flat raw-cut edge, with vertical silicone stripes to lock your hem in place, along with upgrades to last year's fabrics. Seams have been updated to dial in the fit for comfort, so the short tapers to your body for a flattering profile. On top, the bib straps have been re-engineered to help you stay cooler, with stripe-mesh that's built to keep you cooler than before, and lie flat for a sleek silhouette under your favorite jersey. They're finished off with the kind of support from beneath that we expect from Castelli -- the Progetto X2 Air seamless chamois that features buttery-soft surface fabric that's gentle against your most sensitive anatomy, and cushions you with perforated multi-density foam that soaks up harsh vibrations from the road, while allowing sweat to escape so you feel fresh through every mile.