Airborne backpack "RD-54" 30L
RD-54 one of the most legendar backpacks. Firstly it was created for Airborne VDV divisions in 1954 year, but it was so popular, that even KGB units use this backpack in Afghanistan. Modified versions was used by Soviet MVD, Russian Troops in Chechnya and it's still in use in Russian Army and Special Force.
Why it's so popular? Because it's not big 30L backpack, that can be used as simple vest. You can place pouches on straps.
This backpack consist from three parts, main parts for ammo and IRP and two pockets on the side of backpack.
SSO made their own, more modern version of backpack with Molle and from modern materials, but still this is very good old Soviet backpack.