sentences:  The Aimpoint CompM4 is a "tubed" style reflector (reflex) sight that uses a red light-emitting diode (LED) at the focus of a mirror type optical collimator to produce an aligned red aiming spot (what is commonly called a "red dot sight").There are a total of 16 brightness settings for the LED, the lower 7 intended for use with night vision devices and the upper 9 for daylight.The CompM4 is powered by a standard AA battery, and the manufacturer claims that the sight will run continuously for 8 years on a single battery, in its 10th brightness setting.