F-style Mandolin Tuners Packed with Vintage Charm Grover's 409 Series of F-style tuning machines offer an impressive combination of vintage charm and modern reliability. This set of 4+4 tuners is for use on F-style mandolins, with a tight 18:1 ratio to deliver a smooth, predictable rate of tuning adjustment. Moreover, a specially designed adjustable worm gear ensures correct tuner alignment — GearNuts mandolin players find this feature results in a much-enhanced level of tuning stability. Lastly, 409 Series F-style tuners are packed to the brim with old-school vibe, including an open-gear design, rounded washer head buttons, and elegant engraving to pair with your F-style mandolin's refined aesthetics perfectly.Grover 409FN F-style 18:1 Mandolin Tuners Features: Rock-solid 4+4 tuner set for F-style mandolins Specially designed adjustable worm gear ensures proper alignment Open gears and rounded washer head-style buttons for a touch of vintage charm Heavy-duty die-cast base 18:1 ratio provides a smooth,