What size?

the differences are in how the pad is cut and shaped. you dont want pony... pony is made to fit under a youth saddle (14 or 15 inch). prix is for jumping and eventing type work. if you're just pleasure riding or doing flat work you want the A/P style. there's not much difference in the cut of the a/p and the prix pad. A/P is what most hunter pads are considered. (A/P stands for all purpose by the way)