Replacement Clock/Quill Spring For Milling Machines.Fits Bridgeport and most import mills. Clock Spring Housing Must Have Slot - Will Not Fit Housing With Pin! .025" Thick And 1" Wide. Caution Spring Is Tightly Wound - Wear Protective Gear When Installing Spring Into Housing!! Spring Must Be Inserted More Than Halfway Into Housing Before The Wire Is Snipped! We Also Have The Complete Clock Spring Assembly Available In Our Store. We Stock 95%25 Of The Parts For The J Head Milling Machine. Call With Any Questions Shipping And Handling.