MTX solid discs are constructed using one complete segment of Japanese SUS 420 stainless steel then heat-treated to HRC 36+-2. Lightening and drill hole patterns are as per OEM designs to improve braking performance and reduce the temperature of the disc.MTX Discs provide amazing braking control for your motorcycle. All MTX discs are designed and manufactured with world-leading cutting edge technologies:Precision CNC machined and laser-cut technologyJapanese SUS 420 Stainless SteelReplacement for Original EquipmentOEM Design; lightening & drill hole patternsSpecifications:O.D: 220mmI.D: 115mmMinimum Thickness: 4mmDisc Position: Rear Fits: Yamaha WR250 Z 3RB 1991-1993 WR250 Z 4JW 1994-1997 WR400F 1998 WR500Z 1992-1993 YZ125 1989-1992 1994-1997 YZ250 1989-1996