14mm is our standard, 8mm is shallow and 18mm is deep and 22mm is very deep. We are happy to exceed even a 22mm heel cup but that instruction must be specified on the prescription form. A deeper heel cup provides increased motion control, better control of supination or pronation, enhanced proprioception and reduced strain on passive structures. We recommend this modification for plantar fasciitis (suggest also adding varus rearfoot posting). We recommend deep heel cups for posterior tibial tendon dysfunction in combination with a medial flange.