This is a Hi-Viz Sight known as the Magnetic, model M200.
HIVIZ(R) M-Series Ultra-Narrow Magnetic Shotgun Sight. Fits shotguns with ribs from .171" to .265" (11/64" to 17/64") (4.2mm to 6.7mm) . Includes Green and Red replaceable LitePipes in two diameters plus the unique HIVIZ two-toned LitePipes (green LitePipes with a red center).
Features:
Ultra narrow fits ribs from .171 to .265
Green .135 green .175 red .135 and two tone .175
