As a wheelset these zipp 303 clincher disc brake wheels offer the very best in aerodynamics performance and durability capable of riding over various terrains cyclo cross gravel or road they offer exceptional braking performance in the harshest or wettest of conditions and superb performance all year round the zipp 30339s with its firecrest rim technology offers superb aero performance straight line sprinting stiffness great stability in crosswinds and are ideal for climbing also