Wheels - 78mm 80a - Small wheels for good accelaration and manoeuverability. With 80a wheels this particular K2 skate is best suited for outdoor use. Wheels - 80mm 80a - (Exclusive to the Exo Alu) Larger wheels for gliding with ease. With 80a wheels this particular K2 skate is best suited for outdoor use. Cuff - Stability Cuff - This provides better ankle support and flexibility to give more feeling and less strain. Frame - Composite - This particular frame has shock absorbing qualities made only possible by the unique composition of injected nylon and glass fibre. They are a very strong composite design. Frame - Aluminium (Exclusive to the Exo Alu) - Light-weight and a medium length to keep things extremely stable at high speeds while not sacrificing maneuverability, well worth a little extra cost. Bearings - ABEC 5 - Fast, durable, high performance, what you expect from a high quality skate.