1 E--EXTERNAL SPLINE TYPE--- The Shimano GRX SM-RT64 disc rotor delivers powerful and consistent braking performance in all riding conditions. The Center Lock mounting system makes installing and removing rotors quick and easy, thanks to the spine mount and lock ring design.Compatible with both resin or metal padsIncludes external type rotor lockringItem SpecificationsHub/Disc CompatibilityCenter-Lock DiscPad CompatibilityAll Pad CompoundsRotor Size (mm)180Rotor TypeTwo Piece 1209xxx (011a,212-214,)3/24 110722(10: 11/10e:ari--- 31224(10:3/13/24:ari