Castelli Size Chart The best in sleek design and construction, the Free Tri Singlet from Castelli is the ultimate triathlon top. The Velocity Mesh back provides excellent ventilation while you ride or run, and the soft-finish armholes reduce chafing. Two FreeAero pockets are designed specifically to keep your items in place as you ride your bike. Features: - SpeedFreak ventilated race fabric on front - Velocity Mesh back gives wind-tunnel-proven speed on the bike - SnapLock fastener at lower back to clip to Free W Tri Short to prevent riding up during swim or bike leg - YKK(R) Camlock(R) zipper - FreeAero 2 hydro- and aero-optimized pockets - Soft-finish armholes to reduce chafing - Weight: 51g