Fangrui Product Details 1. Finally A Tool That Works - Machined From Zinc Alloy 2. Works On Multiple Styles Of Trems - For Original Fr, Fr Special Fr 3. No More Hours Of Detuning - Make Intonation Adjustments Under String Tension 4. Includes M2.5 Hex Key - You T Have To Find Your Other Hex Key To Loosen The Saddle Screws, We Include One With Every Tool 5. Does Not Work On - Kahler Bridges, Bridges, Bridges With Fine Tuners That Are At A 45 Degree Angle To The Guitar Top Directions For Use 1 - Block Your So It Cant Move (you Can Use Guitars Gauged Wedge Blocks). 2 - Adjust Your Fine Tuners To Mid Way To Allow Clearance For The Toe Of The Tool 3 - Tune The Guitar To Pitch Using Your Favorite Tuner 4 - Clamp The Tool With The Silver Tang Just Behind Block And The Toe Of The Tool Wrapped Under The Fine Tuner Plate (see Picture). Snug It Up. 5 - Loosen The Saddle Screw For Youre Working On. 6 - Your String Is In Tune, Then Fret At The 12th Fret. If The Note Is , Tighten The Intonation Tools Screw, Retune And Check Again. If The N