CNC-machined, steel sight uses eye-catching tritium to provide a fast sight picture in low light and an easily-noticeable, white ring for regular light. White ring is recessed to protect it from being scratched and to ensure proper light reflection from any angle. Available in four different thread diameters to fit your shotgun. Mfg: Marble Arms SPECS: Steel, blued, matte finish. Approximately .32" (8.1mm) long, 3/16" (4.8mm) wide, .21" (5.4mm) high. 3/32" (2.4mm) shank length. See price line for thread diameter. 6-48 Oversize (OS) has a diameter of .146" (3.7mm) which requires a .146x48 tap.