The Formula Four Conical Full skateboard wheels feature Spitfire's performance urethane that lasts longer and withstands more abuse than the competition. Pick which duro you're looking for after assessing the varying attributes, 'cause this is getting technical. FEATURES Quantity Set of 4 Wheels Wheel Profile Wide Surface Smooth Key Features Formula Four Urethane Wheel Shape Conical Full Shape WHEEL PROFILE Wide - More traction and stability at high speed so you'll be less likely to slip out of your line. SURFACE Smooth - Smooth wheels come with a shiny coating on the riding surface that feels grippy at first, but wears away quickly. KEY FEATURES Formula Four Urethane - Unmatched abrasion resistance for fewer flat spots. More controllable grip. Lasting speed no matter the terrain. Smooth anti-slick slide and a longer lasting size and shape. WHEEL SHAPE Conical Full Shape - Wider riding surface and cutaway design for unmatched control and lasting speed.