When versatility is vital, the M-Series line of magnetic sights has you covered. The snap-on magnetic base is available in four different sizes to fit a wide variety of rib widths. All M-Series sights come with green, red, and the uniquely HIVIZ two-toned LitePipe. Pair your favorite shotgun with one of our favorite magnetic sights. Narrow Model (M300) fits ribs from 0.218 to 0.328 (7/32 to 21/64) (5.5mm to 8.3mm). Two Tone Fiber Diameter: 0.175mm. Green Fiber Diameter: 0.135mm. Red Fiber Diameter: 0.175mm.