For those with an AR-platform rifle, or simply any rifle with a top rail, optics are a natural addition. Red dot sights, magnified optics or a reflex sight are all excellent choices depending on your intended use for the rifle in question.
Having backup sights is just good insurance, and the YHM Flip Rear Sight, available from Brownells, is a strong performer at a very reasonable price. With a steel base, aluminum stem and a quick-release button that fosters rapid deployment, the YHM Flip Rear Sight is designed to function with standard AR-15 front posts as well as many other aftermarket front sights (including, of course, the many options available from YHM).
Adding only 2.5 ounces to the overall weight of your rifle and measuring less than an inch tall when folded, the YHM Flip Rear Sight is compact and tough. Two apertures are included, a standard .065-inch and .200-inch diameter peepholes for short- and long-range shooting.