The Pista also comes in a 51cm. I tried both 51cm and 53cm and felt better on the 53cm. I'm 5'8" with a 32" tucked-balls-to-ground measurement (30" inseam pants). Depending on your upper body though you could be either a 51cm or 53cm. I was right on the border but felt the 53cm fit me a tad better.