These were used by the demi gods, the growers in the 1970's to grow indoors, many still do, as they do put out a cheap functional light and very cool too, and 4 feet is a great length to fit in a closet or tent too, most are at about 40 watts and 3050 lumen, thats better than your bedroom cfl,
hang 6 - 8 on a rack, ensure you have a mix of cool white and warm white, adjust the chains daily, fantastic germ and early vegging light, but does require extract grunt come budding, or suffer popcorn buds. ..avoid tubes with gray or blacked ends are these are about to die on you