Designed to offer the user greater stability than a conventional, spherical exercise or therapy ball, the Physio Roll Exercise Ball can be used for a wide variety of exercises but it will only roll in a more controllable forwards and backwards motion.This helps to build user confidence and to focus effort on specific parts of the body without having to worry about lateral balance. This yellow 550mm (21.5\") diameter Physio Roll Exercise Ball, is the smaller of the two sizes available ( a larger 700mm (27.5\") diameter blue version is also available in this section of our shop) but is still very strong with a maximum user weight of 300kgs (47 st), which gives the therapist or physio the option to sit with the user on the Physio Roll Exercise Ball in situations where the user requires more support.