I purchased these over a month ago.The initial set had a rear detent that did not offer a positive open lockup for the sight, which had about a 20 degree range that it could freely move around while open. Being the problem solving type, I attempted to fix it, but could not. The problem didn't get worse, but was not able to be fixed with the minimal amount of material.I emailed Bobro asking if I could purchase a new rear sight base, instead they simply asked for my mailing address and 2 day UPSed an entire new rear sight, which works 100%.More than satisfied with the product, and the customer service is top of the line. You can't go wrong with these sights if you're looking for the lowest profile, lightweight option.