Tightening strap for ski boots and ski boot provided with such strap

Tightening strap for ski boots adapted to be wound in a loop around the cuff of a ski boot to tighten said cuff on the user's leg;

• the tightening strap comprising an oblong flexible element, which is adapted to be wound around the cuff and includes at least one elastic member with auxetic behaviour able to stretch and, at the same time, also to widen in elastic manner when the tightening strap is subjected to traction;
• the tightening strap wherein said elastic member with auxetic behaviour comprises an oblong plate-like body, which has a monolithic structure and is divided into a plurality of contiguous flat sectors, each of which has a macroscopic reticular structure with auxetic behaviour, which is capable of stretching and, at the same time, also of widening in elastic manner when the oblong plate-like body is subjected to traction, and also differs from that of the adjacent flat sectors.