Manufacturer flex ratings are not exact, industry-standardized values. Nor can this guide be an exact assessment of them, but it should give you an idea of the relationship among flexes. In the end, you’ll do your own flex tests, remembering that in a warm ski shop you should be able to squat downward, flexing the boot forward without being thrust too far to the rear.
Flex ratings, from stiffest to softest:
150–140 Ridiculously stiff. For elite male racers.