Stable Ski Boot for large feet. 100 in the X Pro 100 is the flex that is offered, a much lower point in order to ensure that you feel comfortable with a stiff ankle holding your feet and lower leg in place while enjoying the slopes. Notice the 4 clips in order to really lock yourself into the boots, this in order to ensure highest performance. Not made for those with a high forefoot or extremely wide feet. When choosing size, ensure your foot in mm is quite close to the size of the boot, this is to ensure that you are able to use the boots to their fullest.