The maximum user weight capacity is limited to 375lbs. The Reform RX’s smart spine range is tested for users up to 6’7" height.There is no minimum size, weight, or build for using Reform RX. It's one of the most versatile pieces of fitness equipment for smaller or younger athletes. However, the minimum age for use is 13 years.Note: Use of the Reform RX by anyone under the age of thirteen (13) is not permitted.