The FatBead is a large diameter fiber-optic bead replacement sight. This sight features 3mm threads.
Specifications:

Type
Frame Material	CNC Machined Steel
Frame Color	Black
Firearm Fit	Shotgun
Base Configuration	3mm
Style	Dual Color Fiber Optic Front Sight
Front Material	Fiber Optic
Rear Material
Front Color	Green/Red Fiber Optic
Rear Color
Rail Size
Windage Adjustment
Elevation Adjustment
Fiber Diameter	0.120"
Firearm Type