This is the Revell 03084 kit in 1/35 scale, of the ‘Russian Tank Destroyer, SU-100’.
This is the Revell 03076 kit in 1/35 scale, of the ‘Russian BM-13, Katiusha’.
Katyusha multiple rocket launchers are a type of rocket artillery first built and fielded by the Soviet Union in World War II. Multiple rocket launchers such as these deliver a devastating amount of explosives to a target area more quickly than conventional artillery, but with lower accuracy and requiring a longer time to reload. They are fragile compared to artillery guns, but are inexpensive and easy to produce.
Katyushas of World War II, the first self-propelled artillery mass-produced by the Soviet Union, were usually mounted on trucks. This mobility gave the Katyusha (and other self-propelled artillery) another advantage: being able to deliver a large blow all at once, and then move before being located and attacked with counter-battery fire.