For Sportster rear, 1979-1991, left side, 11 1/2 inch disc. Machined from 420 stainless steel plate, these brake discs are heat treated for strength, wear resistance and hardness. Precision ground for trueness, these discs are drilled to reduce weight and provide cooling while reducing brake fade under extreme conditions. These discs have a unique style, increased friction coefficiency and excellent wear characteristics. Complete hardware kit #57123 (flat head allen).