This is a Hi-Viz Sight known as the CompSight, model PMLW01.
HIVIZ(R) CompSight(R) LiteWave(R) Shotgun Sight. Screw-Attach design replaces the front bead on a shotgun. Fits most vent-ribbed shotguns with removable front bead. Includes three Green" three Red and one White replaceable LitePipes in three diameters.
Features:
Fits most vent-ribbed shotguns with removable front bead
Three interchangeable LitePipes red green and white
