The priority for combining the _friction properties when two shapes come into contact. If the priority of one shape is higher than the other shape then the higher priority _frictionMixing will be used. If the priority of both shapes are the same then simply the higher enumeration value of PhysicsMaterialCombine2D from both shapes will be used. This is assigned to the current _surfaceMaterial.

public ushort frictionPriority { get; set; }