Check the listing for details. Callaham American Professional Premium Upgrade Kit. Condition: New. Listed at 138.75 USD. This kit is for the new for 2017 Fender American Professional bridge. Although touted as a new and improved model, it still uses the powdered metal block typical of Fender's mass production models. This kit replaces the powdered metal block with our renowned Callaham Enhanced tremolo block, produced from cold-rolled American steel, and featuring our proprietary zero-clearance bushing. This is then paired with an included Callaham Virtual pop-in Tremolo Arm. The kit also includes a set of Callaham Vintage Style Stamped Steel Saddles with stainless steel screws and springs. Lastly we provide tremolo springs that are superior to those provided by Fender. Callaham American Profession Block Enhanced With a 64 virtual pop-in trem arm & parchment tip Callaham Vintage Stamped Steel "CG" Saddles for American Professional bridges with stainless steel screws and springs 3 Stainless steel top plate screws 4 Tremolo Springs Allen Wrench