The Honeywell Boiler Trim Kit is all you need for your hydronic needs. Save time by ordering one item instead of several different parts. It's a complete time saving solution in one handy box! Kit Includes: Expansion Tank - Welded, not clamped, for longer leak-proof life, 4.4 gal tank. Butyl diaphragm to separate the air from the system water. Check Valves - Allows replacement of expansion tank and/or air vent without draining the heating system. SuperVent Air Eliminator - Optimal air removal from hydronic systems. Eliminates annoying gurgling sounds. Debris baffle to control dirt fouling and prevent failure. Dial-Set Boiler Fill Valve And Backflow Preventer - Easy dial-set technology allows simple output pressure setting in psi. 1/4" NPT port on side for optional gauge. Includes union nut, sweat, and threaded tailpiece.