Heavy Duty EVA foam rollers are made from a dense “closed cell” foam giving them an extra-firm feel. Perfect for positioning, balance, postural and muscle re-education, spinal stabilization, body awareness and coordination, and ranging and strengthening activities. Round rollers offer progressive exercise sequences - user can move from an easier (smaller diameter) to a more difficult (larger diameter) roller. Half round roller is a great tool for ankle stretching and knee rehabilitation. A Half round foam roller is a great tool for ankle stretching and knee rehabilitation. Use half roll as rocker board by standing on flat side. Diameter refers to the width of the half-round profile.