The Long Bead by Truglo is CNC-machined, and it's the industry's favorite bead replacement. This shotgun sight green, with a fiber of 0.078" in diameter and 0.5" in length.
Specifications:

Type	Fiber Optic Bead
Frame Material	Metal
Frame Color	Black
Firearm Fit	Shotgun w/Vent Rib
Base Configuration	3mm
Style
Front Material	Fiber Optic
Rear Material
Front Color	Green
Rear Color
Rail Size
Windage Adjustment
Elevation Adjustment
Fiber Diameter
Firearm Type	Shotgun