Pretty much what the title says, anyone have any experience with them?

sorry, wrong forum title...

My bad I was gonna get them for a glock 21, I'll see if this can get moved

You mean the rds mount?

It's great. It still fits in its kydex holster. I didn't have to mill the slide and buy tall sights.

A guy I shoot USPSA has one, seems to work perfectly.

Do you mean their iron sights or RBU mount?

I have both. The irons are great if you like a wide rear notch. My only complaint is no serrations on the rear sights. Other than that, they're nice. Black nitride coated as well.

The RBU is awesome enough that I won't spend money sending off a gun to be milled.

The BUIS on the mount are good to 25 yards, and I had no issues hitting man sized targets at that distance with them. The mount is solid and holds zero precisely.  Have had zero issues whatsoever. Would be perfect for duty use if my agency allowed RMRs.