This is a Hi-Viz Sight known as the TriViz, model TT1001.
HIVIZ(R) TriViz(R) Front & Rear Shotgun Sight Set for turkey or deer hunting. Fits vent-ribbed shotguns from 1/4" to 3/8" (6.3mm to 9.7mm) with removable front bead. Patented design features a rear sight with two Green LitePipes. The front sight includes four Green replaceable LitePipes: three triangular shaped in three different sizes to adjust for elevation; one round.
Features:
Green front
Green rear
Fully adjustable
Fits vent ribbed shotguns from 1/4 to 3/8
Triangular shaped LitePipes (3 in different heights) and round