夜視鏡
A side-rail on the left wall of the receiver accepts various telescopic sights and night optics. The standard daylight telescopic sight for the M91 is the ZRAK ON 6 × 42. For low light conditions the rifle can also be equipped with PN 5 × 80 passive sights of the first and second generation of Night vision devices. The optical sight can be removed from the rail and reinstalled without loss of zero.