This Webster Clock Mainspring Winder will unwind and wind mainsprings. It allows for the safe removal and installation of both loop and hole end clock mainsprings. This deluxe kit includes 2 hooks, 9 mainspring sleeves (1" to 2-1/4") and instructions. AN absolute must item if you are going to be working with mainsprings. NOTE: This unit is the new and improved version with the new arbor support.