It is incorrectly displayed as being the standard issue grenade of the Red Army when in reality, it would have been the more updated RGD-5 or other newer grenades. It is similar in appearance to the American MK II "Pineapple" grenade.
John Rambo first encounters the F1 grenades when they try sneaking under a trip wire fence, only to find that the wire is attached to the live grenades. Rambo narrowly stops them from detonating and killing them all by holding the pin in the grenade while Hamid crawls under the wire.
The grenades are later seen when Sgt. Kourov and Rambo get into an intense fight above the cave. Rambo manages to prevent his spine from being broken by pulling the pin on one of Kourov's F1 grenades strung up on his uniform. This distracts Kourov, who lets go of Rambo so he can pull the grenade off his uniform before it detonates. Rambo kicks him, however, and Kourov falls into the cave as the grenade explodes, killing him.