Iris Front Sight adapts easily to varying light conditions and target sizes due to 2.8 - 4.8 mm diameter range. Fixed ring width. To meet individual preferences the shooter may set either cross hair or lateral bar; special tool included. Optionally a larger front ring may be used to achieve better target coverage. - M18 x 0.5 thread, fits ANSCHÜTZ, Walther and Feinwerbau 601.