Folds down when not in use. Strong spring secures sight in “up” or “down” position. The reversible notch piece gives choice of “U” or “V” notch. Three styles and two heights of these sights are available and fit most standard rear sight dovetails. The chart shows the overall sight height for those sights below. 69 - Height, .360" (9.1mm) to .490" (12.4mm).