Allows use of iron sights with scopes up to 40mm lens diameter. Does not include arrestor pin.2 Piece Mounts.Base Fitting: 9.5 - 11.5mm (3\8") Dovetails - Most popular size (suits most modern airguns & .22 rimfire rifles).Tube Size: To fit 1" (25.4mm) diameter body tube scopes.Front Lens Size: Up to..