Plain 18-inch winding bars in 1/2-inch diameter steel. These are the basic round-profile bars for winding and unwinding torsion springs. They get the job done on standard residential springs where you need reliable leverage and a good fit in the winding cone. The 1/2-inch diameter fits most standard residential winding cones, but check yours before buying because some cones take 7/16 or 5/8-inch bars. At 18 inches, you've got enough leverage for lighter springs. For heavier springs, consider stepping up to 24 or 36-inch bars. Torsion springs are under extreme tension so use proper bars, never a screwdriver or rebar.