Zsh1-2 is proven to stop a round of 5.45x39 from an aks-74u. K6-3 helmet+visor are Titanium and outright deflect FN 5.7 from a P90. (K6-3 is an Altyn helmet without a radio system). These are a pretty rare find here, they are nothing like the shitty 6b47's, Zsh1-2M is made of Aramid kevlar layers covered with an aluminium outer layer/shell to take the initial impact and slow the bullet for the aramid to then catch it, it will eat FN 5.7 rounds with only barely noticeable bulge deformations to the aramid (resulting in only very low chance of Knockout). The suspension system keeps the head away from the aramid.
K6-3 is a greater powerhouse against handgun calibers due to its titanium visor whilst the ZSH1-2 is more potentially capable of stopping an intermediate caliber round due to the aramid layer being present if 5.56 isnt deflected. Oxide on Youtube stopped an AKS-74u round with the ZSH1-2. The visor on the ZSH1-2 and the small view slit on the K6-3 are rated for 9mm.
You won't get similar protection from western helmets due to most of them being only rated for level IIIE, be it the MICH or PASGT. Meaning 9MM to .38special protection at best.
These two helmets truly are the pride of Russian anti-terror forces and Spetznaz, they're on the Verge of being western rating level IV, they offer truly formidable protection.