Magnum 57mm Freestyle Wheels

Magnum 49D, 53D, 57D, and 60D standard frestyle wheels provide a range of grip and roll at a less expensive price Giotto and urethane counterparts). This is still a high quality wheel, which is used on many types of skating surfaces including standard wood floors coated with plastic or polyurethane, tile type basketball and volleyball courts, indoor and outdoor tennis courts and concrete or terrazzo surfaces. Many competitors use combinations of hardnesses of the Magnum for training to achieve the best skating result. The RollLine Magnum is a medium-profile, durable wheel which is strong, light, and has extremely close tolerances for roundness, trueness, and for the cage where the bearings andspacers are mounted. 
The tread color identifies which hardness the wheels are.
Grey = 49D
Cream = 53D
Yellow = 57D
White = 60D
 
Set of 8 wheels
 
The softer the wheel, or lower shore “D” hardness number, the more the grip and slightly less roll. The harder the wheel, or higher shore “D” number, the more the roll, with slightly less grip.  The shore “D” scale is used for rubber and plastics, while the shore “A” scale is used for urethane.
 
It is almost always recommended to use spacers in the wheels, when using standard 7mm bearings.