A family of lamps having a Multifaceted Reflector and measuring 2" (16 x 1/8th") across the face. Although technically an open-face lamp containing no lens, often thought of as the smallest of the PAR family (although the MR11 is smaller, but much less widely used). In entertainment, the lamp is most often found in the Mini-Strip and PAR16/20 can (birdie). Available in a wide range of voltages, wattages, and beam spreads.
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http://www.residential-landscape-lighting-design.com/mr16-lamps-bulbs.htm