One rackmount tube cavity with air cooling system as shown Neat setup pulls air through 2 foam filters on front into the 6 cooling tubes that enter the cavity There is a fail safe air movement switch on top of the cooling output that presumably tied into a system to shut down or alarm if air volume drops. The cooling system pops off the cavity via the 5 screws. There is also a removable cover on the input tuning and coupling end of the cavity. Build your own transmitter! Standard rack mountable It is not a complete transmitter system and we have no way to test it other than the cooling fan, so no guarantees May be missing a screw or two or other accessories, see all pictures NO tube in it, see our other listing for a 3CX400U7 that came out of it. Fairly clean, note the cavity section is not dirty, but rather is silver plated and thus tarnished as silver does. Surplus deal, History unknown All sales final