Booster Straps are designed to make a ski boot flex more evenly. They come in four different flexes, Kids, Soft, Medium, and World Cup. The different flexes allow a skier to stiffen or soften their boots all while helping to smooth out the boots flex. -Stiffer boots give you better rebound, which helps in keeping you centered on your skis. -Softer boots allow for a greater range of movement and can help in reducing shin bang. Depending on your intended goals, Boosters can be used to replace your power strap or be used in conjunction with them. A proper bootfitter can help you install your straps as well as find the right Booster strap combination for you.