These brushes are 13" inches in diameter and fit our Viper AS6690T 26” automatic floor scrubber and our Viper Fang 26T automatic floor scrubber. 2 are required for the machine to scrub any floor. The poly bristles are of a medium-duty, for scrubbing any type of tiled floor. Our auto scrubber brushes are great for cleaning the high and low parts of any uneven floor. Take a look at our auto scrubbing procedures for more hints and tips on how to properly scrub your floor.