A prosthesis, for example a breast or a finger prosthesis, is formed for mating with a first body portion of a user such that the prosthesis is symmetrical with a second body portion of the user. The prosthesis is formed at a manufacturing location using castings of the first and second body portions which the user creates themselves at a user location separate from the manufacturing location using a user casting kit. The user casting kit includes casting material, skin colour samples and any additional tools required for the subsequent manufacture of a custom prosthesis without the user being required to leave the user location.
