Designed for an adjustable brake, the H6 Leading Edge heel is a H5 rubber heel with a hook-and-loop attached strip of slide material across the front edge to ease the transition from sliding to stopping.
It's packaged with three edge strips: (slow) S2 - for little slide before the brake, (medium) S4 - for more slide before the brake, and (fast) S6 - for the most slide before the brake.