Ummm- The RPG is a rocket propelled grenade. It is a large rocket fired from a rocket launcher. It is not fired from an SKS.
The Yugo has a RIFLE grenade launcher. They fire a standard 22 mm rifle grenade. Same as the US M14 rifle, or the M1 Garand.
Here is what the Commie grenades looed like- http://www.inert-ord.net/yugos/yughr/m60/index.html