The RD-4 grenade launcher, alternatively referred to as the radiation launcher, was a grenade launcher model produced by Merr-Sonn Munitions, Inc. that launched radiation grenades. This launcher allowed for fuse customization of the grenades, enabling detonation upon impact or delayed explosion after bouncing. During the initial stages of the Clone Wars, Confederacy of Independent Systems OOM pilot battle droids utilized this launcher in battles like the First Battle of Kamino and the Battle of Rhen Var. Towards the war's end, the IG-100 MagnaGuards also began employing it.
In Star Wars: Battlefront, the RD-4 grenade launcher functioned as the pilot droid's exclusive main weapon. Star Wars: Battlefront II saw the pilot class renamed to the engineer class. Instead of each faction's pilot unit having a unique primary weapon, the engineers were given a standardized shotgun as their main weapon. Consequently, the MagnaGuards, a specialized unit, inherited the radiation launcher as a secondary weapon.
The weapon's design, similar to other grenade launchers in the series, is derived from the T-21 light repeating blaster.