A well machined dual aperture, same plane so your zero is unaffected. No burrs or defects. Note that it has a large peep sized at .230, small peep at .100, so it's slightly oversized from the milspec of .200/.070, but I happen to like the XS size because you do get increased visibility and lighting at the theoretical cost of slight accuracy, so the tradeoff is worth it. Screws into mil-spec rear sight hardware without issue. Great to have this option.
One of the best things I've added to my S&W M&P-15! Now I can switch between apertures, and the POA and POI doesn't change all over the place.
Looks great, zeroed well, the larger aperture works great with a red dot co-witnessed.