This is a turbine blower. It fits 540-sized Motors (like KV 3570) with a diameter of about 35.8 mm and 25 mm pitch cicle diameter. Mine runs with a brushless KV 3570 @ 12,000 rpm. And yes, it blows like hell. :-) There are two types of housings. One with stands, and one without stands. The turbine rotor fits on both, of course. The inspiration came from http://www.thingiverse.com/thing:39755. Have fun. UPDATE 02.2015: Re-modeled the Rotor: Enhanced geometry, easier to print. Even better efficiency (tested it with 22,000 rpm ~ 350W). Re-modeled the Housing, both "Gehause" and "Basisplatte": Feet are now shorter (thanks to Brian aka. 58webbing for the hint); reinforcing ribs on the baseplate(s) have been new arranged; some minor cosmetic repairs. Renamed the files, remöved umlauts. :-) Update of Update: Added one more Rotor. It is more sturdy and fairly easy to print, even with .6 mm nozzles and extrusions like toothpaste. Changed the center hole of the mounting plates to match 13 mm diameters of 540 bearing covers. Once again some cosmetics. Update of Update of...: :-) Two new Rotors. I took down the old Designs as they were not efficient enough. The new ones run much quiter and have about 19% more throughput. Wir the 92-22-type I can achieve about 295m³ per hour @ 6,5A / 24V.I printed mine with 0.1 mm layers. This is recommendet at least for the rotor, as it has some sharp edges on top of its fins. Before going to high rp/m, check if your rotor turns free and is not way out of balance. When your printer is well calibrated and your filament has not the shape of cooked spaghetti, you don't need to balance the rotor at all. If you have to do some balancing anyway, try this by drilling 1 mm holes through (!) the base of the rotor. Don't even think about glueing somethin on top.