Bones STF Side Cut 56mm V5 Skateboard Wheels (Set Of 4) BONES WHEELS STF Side Cut 56mm wheels. Street Tech Formula (STF) is specifically engineered from top quality components to obtain all the best properties necessary for the ultimate in street wheel performance. VERSATILE, LIGHTER WEIGHT, LESS SIDE DRAG, FASTER LONGER GRINDS,HIGH RESISTANCE TO FLATSPOTS, GRAPHIC PROTECTION. Good for LEDGES, RAILS, BOWLS.