“The severed tail of a radscorpion.”— Fallout in-game description
A scorpion tail is a miscellaneous item in Fallout, Fallout 2, and Fallout Tactics.
They are the tails taken from dead radscorpions, cut at the base where they meet the body, and they are prized for the poison sac it contains, which is used to make a poison antidote. The tail is comprised of the segmented sections of the tail ending in the stinger, they vary in size depending on the radscorpion.
Razlo in Shady Sands uses them to make the antidote.
Myron in the Stables can use the tails to make antidote.