reinforcement for your boot. the deeluxe flex booster 1k strengthens your boot when you need it and also ensures longer life.want to use your jib boot for a kicker session, or need a slightly stiffer flex in the backcountry? the flex booster remedies this without you having to change your boot.1k boosterwith the flex booster 1k, the flex and support of the boot can be adjusted so that it becomes a little stiffer and has more response. this allows you to make your boot one point harder on the flex rate.