According to the sporting regulations, there is no restriction here. If the length of the prism rail of the system is not sufficient to achieve an optimal eye relief of the diopter, it may be extended in the desired direction by means of a sight extension . The front sight must not protrude beyond the apparent muzzle. Otherwise, the ISSF rules 7.4.2.3 Sights apply, taking into account the national exceptions for age and senior classes.