These brushes are 12" in diameter and made of polypropylene, a great material for everyday scrubbing on practically any commercially finished surface. Will not harm tiled floors. These floor scrubbing brushes are made to paired together to fit the Powr-Flite Phantom 24" traction drive automatic floor scrubber. The brushes come in left and right versions, so be sure to pick up both if this is your first time buying. Great for use with floor cleaning degreasers and floor cleaning soaps & solutions.