Sidolówka (pron. seedoloofka) was an unofficial, yet common, name of the R wz. 42 hand grenade, produced by the Polish resistance organization Armia Krajowa in occupied Poland during World War II. The name of the grenade came from Sidol, a metal-cleaning agent from Henkel sold in Poland at the time. The first grenades used the Sidol bottles as the casing. Later on the casing was purposely modelled after the bottle in order to allow for easier hiding of the weapon.