These objectives will be met over a three-year period. The initial phase of the proposed work will use an iterative engineering design - modeling - evaluation process to develop variable compliance elements and an industry standard pylon mount adapter. During the second phase of the proposed work, clinical evaluations of SFF prosthetic sockets will be studied. The effectiveness of variable compliant elements in enhancing comfort and fit will be determined using a within subject case comparison study of SFF sockets with conventional laminated sockets. Durability of SFF sockets that incorporate an industry standard pylon mounting system will be determined during a 12-month clinical field trial.