You would need to know the year/model of your bike if you bought an OEM
one, I guess there's stuff you'd need to know if you bought an aftermarket
one too.
STD/Tourer - 97-99 - one kind
Interstates and all 2000+ bikes - another kind
I got a good cheap used one from a crashed bike with low
miles... Here's one from Pinwall with 45K on it - $90... mine
had less miles and was cheaper, but this one is probably good...
check out the micrometer picture, no lip...
http://www.ebay.com/itm/99-03-Honda-GL1500-CF-Valkyrie-00-01-C-CT-CD-Valkyrie-REAR-BRAKE-DISC-ROTOR-/131609814905?hash=item1ea48e6779:g:-CsAAOSwQPlV-b9t&vxp=mtr-Mike