I have bought 5 sets of those A1 rear sight kits lately from 3 different sources. Most are identical and I assume are coming out of the common Cerberus source from China maybe? These are the only ones I can find out there except for the big $$ stuff at SAW. At the range, flipping the sight did not change the elevation, but moved the grouping in azimuth - there was some flyer overlap obviously, but the groups were definitely left-right challenged. Back in the shop careful measuring verified my suspicion - they are drilled coplanar, but not drilled horizontal off-set to account for the 90 degrees of rotation on the threaded sight screw! WTF?!?! Has anyone else encountered this? Sure, you can fix this, but thought I would warn the hive.

this explains and verifies my inability to get good groups at long/short w/my latest build. was tearing my hair out.... I checked my aperture which is from a DPMS kit, and compared it to an old Colt and you are right - all i have is a caliper, but the L aperture is obviously drilled higher and offset left-right from the other hole. The DPMS long is unmarked and they are definitely not offset in el or az....

Sneaky Chinese ....They don't want us to hit anything.