Magpul has introduced a metal BUIS with elevation adjustment known as the MBUS Pro LR. The sight looks good, and I particularly like the scalloped face which will aid in blocking reflection or glint. MSRP is $129, so it’s a direct competitor with other well-known sights such as the MaTech, GG&G, and Knight’s Armament 0-600 rear.
The KAC 0-600 is long-held to be the gold standard of folding, range adjustable buis. It has finer adjustments than the Magpul offering from what i can see, but the Magpul has one trick up its sleeve to offer a bit more utility to the shooter: the aperture can still be switched from a large or small aperture. This is a fantastic feature as a small aperture is near useless at night.
Calibration at this point is unknown.
This is a cutting edge piece of equipment and I hope to get my hands on one soon.