Hi-Viz Magnetic Sight, Fits Narrow Shotgun Rib .219-.312, 4 Color M300 HIVIZ(R) M-Series Narrow Magnetic Shotgun Sight. Fits shotguns with ribs from .218" to .328" (7/32" to 21/64") (5.5mm to 8.3mm). Includes Green and Red replaceable LitePipes in two diameters plus the unique HIVIZ two-toned LitePipes (green LitePipes with a red center).