HIMARS mobile MLRS system.
Most of the damage done by both sides is artillery. Most of the artillery is Russian, with the same range and abilities, Russia just has more of them. It is plainly obvious that the HIMARS using longer ranged, GPS guided missiles, are going to reduce Russia's numerical artillery advantage.
They are descendants from the MLRS used in both Gulf Wars, which were designed to take out Russian tank formations in Cold War scenarios. Russian state media and cheerleaders are going nuts over this. Claims of how these are going to target Russian territory and Russia will have to escalate, etc, just show how worried Russia really is about these. They know exactly what these can do to their equipment heavy, personal light BTG formations.