rollerblades

Otherwise known as Death on Wheels.1)2) They may only be worn with tight neon leggings and/or a nylon workout suit.3)

1)
Four wheels, to be precise.
2)
Per foot, that is. Unless you have a strange pair of rollerblades. Could be 3 per foot though.
Of course, if there were one for every three feet, they would no longer be rollerblades, having turned into yards.
3)
Unless, of course, you're Batman, in which case your leggings may be black.