The Seba Brake Kit can be used to add a heel brake to a huge range of frames, up to 255mm (axle-to-axle). If a frame has a max wheel size 84mm or smaller, this brake will generally fit. It comes with a set of bolts that you use to replace the ones that come on the skate.
Please note that this is the short brake kit and does not work on the 273 (90mm) frames. For those skates, you will need the Long Brake found here.