The Strassburg Sock is designed to be worn at night while sleeping, or during periods of extended rest. For optimum results, the sock should be worn for a minimum of 6 hours per night until the sufferers has 7 pain free mornings. In an independent medical research study, the largest every conducted on any night splint this was an average of 18.5 days and 97.8% of patients recovering within 8 weeks. The Strassburg Sock - REGULAR SIZE (Fits calf size up to 16 inches) (Measure AROUND calf at the widest point.)The Strassburg Sock - LARGE SIZE (Fits calf size 16 to 21 inches)(Measure AROUND calf at the widest point.)The Strassburg Sock - PEDIATRIC SIZE (Fits calf up to 12 inches)Fits calf size up to 12in around. Intended for use by children with cerebral palsy and ankle equinus. Generally for children from about 2-8yrs old. The regular size may be more appropriate for children above this age.