Comparing & Contrasting 3 Back Frame Options for a Rigid Ultra Lightweight Wheelchair The two primary types or styles of ultra lightweight wheelchair frames are folding (x-frame folding cross brace) and rigid (box or open frame). Within the two overarching groups of ultra lightweight wheelchairs, there are a number of options available in each to lead toward the selection of the most appropriate wheelchair for a user. As a part of the complex rehabilitation technology (CRT) interdisciplinary team, it is important that you have an understanding of how these options could potentially impact a user's ability to propel his/her wheelchair in the most efficient and healthy way possible. 3/29/2019 Keep Reading