Same benefits as the R4 model, with increased tilt angles • Balance on the large 4? center ball, or remove and balance on two wooden balls attached to bottom of the board • Excellent sports trainer • Use for calf stretch, push ups, or sit and wobble • Beg/adv. model includes 3? ball (beg.) and 4? ball (adv.) • Dimensions: 15? x 7.5?