They were archers who could use either the right or left hand, both to sling stones and shoot arrows from a bow. They were Saul’s relatives from Benjamin:

Choose thee, either three years of famine, or three months to be destroyed before thine adversaries while that the sword of thine enemies overtaketh thee, or three days the sword of Jehovah and the pestilence in the land, and the angel of Jehovah destroying through all the borders of Israel. And now consider what word I shall bring again to him that sent me.