This is a Hi-Viz Sight known as the Magnetic, model S300-G.
HIVIZ(R) Narrow Magnetic Shotgun Sight. Fits shotguns with ribs from .218" to .328" (7/32" to 5/16") (5.5mm to 8.3mm). Features one Green" non-replaceable LitePipes.
Features:
Narrow model
Green non-replaceable Litepipe
Fits ribs from .218 to .328
Round shape
