Cube reaction hpa sl 29 hardtail bike the reaction hpa sls extraordinarily refined design combines maximum performance with the highest possible quality the superb aluminium frame in combination with top quality components such as the complete shimano xt 2x11 group and the superlight fox 32 float suspension fork makes it ideal for both xc races and multi day alpine rides the 29 wheels allow you to carry high speed over a great variety of terrain framethe reaction hpa it stands for high pe