Floor tom converter kits convert a floor tom into a bass drum for a Club/jazz setup if you want to reduce the size of your kit for a particular venue/scenario.
The
Gibraltar seems to be the best one that I've found, mostly because it includes an accessory to mount a rack tom on the converted floor tom, just like a 4-piece kit eliminating the need for a separate stand, which is the point of the conversion kit in the first place: to make the kit smaller... The spurs also look very industrial.