These inexpensive packs of 8-40x3/8 extra large diameter head machine screws, are great to keep in home, in the field and at the rage.8-40 is a very common factory thread in the gun world, for scope mounting, fits most major manufacturer rings and/or bases (usually bases)Including but not limited to:Leupold, Weaver and Burris, that feature provision for 8-40 UNS threads. Screw features: 8-40x3/8 head0.224in (5.7mm +/- 0.1) head diameter0.1in (2.6mm +/- 0.1) head height0.375in (9.52mm +/- 0.25) thread length0.35in (12.12mm +/- 0.25) overall lengthEach pack contains 12 Pieces Designed for rifle scope base mounting, sight fixing, two piece scope mounts, weaver bases, and even some pistol and shotgun applicationsMay be trimmed by gunsmith to suit.NOTE may require reduction of the head and/or length for some applications, first image shows screws oiled for corrosion resistance, all measurements areapproximate