This is a set ( 3 on a side) of genuine Grover Rotomatic(R) tuners in chrome, part number 102-18C, new and blister packed. Gear ratio is 18:1 with precision cut worm and gear for perfect meshing, eliminating backlash and slippage. The higher gear ratio provides for finer tuning and greater stability. Gearbox is permanently lubricated and countersunk tension screw permits the player to regulate the tuning tension to custom feel. Post hole size is 25/64". They are a perfect replacement for your existing tuners on most guitars. Please check your guitar for mounting screw location, post hole size, and headstock thickness. All essential hardware and screws are included. Upgrade that acoustic guitar with some new hardware today! Some modifications could be needed. Take off the old ones, put in the new. These come with a lifetime factory guarantee. Return to Grover for a free repair or replacement.