The Glo-Dot Universal fiber optic sight by Truglo is a .120" diameter red front sight. It is compatible with a ventilated rib barrel.
Specifications:

Type	Fiber Optic Front
Frame Material	Metal
Frame Color	Black
Firearm Fit	Shotgun w/Vent Rib
Base Configuration
Style	Fiber Optic Front
Front Material	Fiber Optic
Rear Material
Front Color	Red
Rear Color
Rail Size
Windage Adjustment
Elevation Adjustment
Fiber Diameter	.120"
Firearm Type	Shotgun