1 15/16".This is a used spare so that may be a little loose but not much.Went through this last year looking for a cheap auto replacement or something.Save your energy,there ain't nothing.Replaced all 3 with SLP pieces.Perfect fit and still look great for a lot less than Yamaha.
They don't appear to have the duel bevel like the OEM Yamaha and they're listed for Viper (and AC) but if they're the right I.D. and O.D. perhaps they'd fit an SRX.