Upper limb amputation causes several functional disabilities and lowers patient’s self body image. At Delft University of Technology the WILMER Open Socket has been developed for below elbow amputees. It allows easy donning and doffing, and minimizes perspiration problems by leaving 75% of the skin uncovered. However, the relative large locking mechanism and the bulky structure of the socket degrade the cosmetic value of the prosthesis and can result in reduced wearing. The aim of this study was to design a new WILMER socket that fits closer to the skin and is more aesthetically pleasing. A new design was also made for the locking mechanism to reduce the thickness of the socket for children and patients with long and thick residual limbs. The final design and the prototype of the locking mechanism have a height of 7.2mm, which means that a reduction of 6.8mm has been achieved. The new WILMER socket was made out of stainless steel wire mesh. The socket has a smoother transition between the arm and the limb (