24-inch hex winding bars, 5/8 to 1/2 inch, part number 587. The extra six inches over the 18-inch version makes a noticeable difference in leverage, especially on heavier springs where you really need control over each quarter-turn. Hex profile keeps the bars from rolling when you lay them on the ladder shelf, which is one less thing to worry about when you're up there with a wound spring. These are 5/8 to 1/2 inch, so they fit the larger winding cone holes you'll find on heavier-duty residential and some light commercial setups. Check your cone size first.