Two-Bearing Quill Upgrade Kit (For All MARKs) (555088) \n \nTwo Bearing Quill Upgrade For all MARK�s with Poly-V Belt Systems. The Two-Bearing Quill Upgrade makes your MARK run smoother - eliminates runout and wobble. Early MARK V 500's made before 11/01/84 were produced with a single bearing quill. Single bearing quills this old have a worn bearing. This wear creates runout and wobble that will jeopardize the precision of your drilling, turning, sawing and other operations. This Two Bearing Quill Upgrade will solve that problem and improve your results on every project. Even if you own a newer Machine wnd are a moderate or heavy user, your quill may be worn out. This Two-Bearing Quill Upgrade will greatly improve the performance of your machine too. The Two-Bearing Quill installs in your Smart Motor easily in less than an hour by following the detailed instructions. \n \nFits: MARK?7 and MARK V units with the Poly V drive system (starting 1960). \n \nNote: Not compatible with Shopsmith ER or M2. Will not fit older Mark V units with the Gilmer drive system.