The Hornady zip spindle kit is the ideal kit for updating your older Hornady sizing dies to utilize the new threaded spindle design. The zip spindle design on all full length size dies positively locks to eliminate slippage. A Series of light threads cut on both the spindle and spindle collet allows you to make incremental adjustments by turning the spindle or you can easily zip it up or down for larger movements. This kit includes a new threaded spindle and a threaded spindle collet. To install, remove the non-threaded spindle, collet, and expander ball from the existing die. Re-attach the existing expander ball to the new spindle, and install the threaded spindle and threaded collet. If the spindle on the expander die is already threaded, then this kit is not necessary.