An interchangeable lock-pump prosthetic system that includes a universal dummy, vacuum pump, and mechanical lock. Each of the three objects have similar geometries for the purpose of fitting into a prosthetic, whereupon a user may for instance, swap the vacuum pump with the lock, depending on the needs of the user and without changing to a separate prosthetic. The universal dummy is an inactive component and acts as a placeholder during manufacturing of the socket, for the eventual inclusion of the vacuum pump or mechanical lock. The vacuum pump is a pressure dependent object that acts to remove any residual air between the socket and the elastomeric liner. The lock takes advantage of a mechanical locking pin which receives a properly configured liner, thus securing the user within the prosthetic socket.