These replacement brushes are sold as a set, one black and one red. They fit all the Beck Polishers and some Dremel machines.
A little change, I didn't get the red ones this time I have black and burgundy available.
To help you determine the fit, the cones that hold the brushes are, 3 1/2 inches long. The circumference of the largest circle end of the cone is 9 1/2 inches. The circumference of the smallest circle end of the cone is 4".