Comes completely pre-assembled, ready-to-use, compatible with any Ameda electric breast pump, designed to prevent milk backup into tubing, includes optional reducing insert. Includes, instructions, (1) adapter cap, (1) diaphragm, (1) pump body, (1) insert, (2) valves, (1) locking ring cap, (1) 4 oz bottle, (1) tubing adapter, (1) tubing