They are excellent quality and maintain position. Also absolutely no vibration blur. I’d buy them again in a heartbeat.
I can say the same thing about the Kemimoto ones I bought off of Amazon for $30.
Ok, maybe not 'Excellent' quality, but more than sufficient, stay in place, no vibration blur and managed to survive a low speed oopsie with minimal damage.
I've handled the RE mirrors and they're fine, but I don't really think they're worth the ~$80 they go for on eBay, let alone twice that from a dealer. They just don't seem that much better to me.