The hand grenades used by the German Army are all of the "offensive" type: that is, they have a thin metal casing with a high proportion of explosive filler. Being of this type, they depend on the blast effect, instead of on the fragmentation of the case as in the U.S. "defensive-type" Mills grenades. They can be used safely by troops advancing erect in the open, because they can be thrown to a distance greater than their effective bursting radius. The model 24 and model PH 39 stick-type, or "potato masher"-type, grenades are used more often than the "egg"-type and can be regarded as the standard hand grenades of the German Army. In addition, there is a smoke stick grenade which differs from the regular stick, or "potato masher," only in the marking on the head of the grenade.