While Pre-Contouring is a very effective design technique, it can be difficult to execute because humans vary in size and shape, as well as the quality and amount of tissue surrounding the bones we sit on. Cushion widths relate directly to the overall width of the individual and their wheelchair. A paraplegic individual may have very little tissue outside of their trochanters. So, their overall width may closely relate to their bi-trochanteric width. Conversely, another person may have considerable redundant tissue lateral to their trochanters and therefore have a much smaller bi-trochanteric width relative to their overall width. Since loading of the trochanters improves stability by widening the base of support and reduces the load the tissue that supports the Ischial Tuberosities must bear, designers must understand the anthropometry of the pelvis to design an effective cushion.