Nobody upgrades the rear rotor. It is the brake you use without thinking about it, settling the bike into a corner, holding a line down a loose descent, keeping five hundred pounds of motorcycle still at a light on a hill. It only gets your attention the day it starts to pulse under your boot.
By then it has been fading for a season. The Galfer Rear Wave Rotor is a direct replacement, cut from the same virgin high carbon stainless Galfer has been making brakes from since 1952, in the same factory outside Barcelona.