Compatible with Black and Decker models: GH3000 LST540 GH3000R LST540B,easy to choose the right spool for your trimmer Easy Installation: simply push this trimmer head into the string socket and it automatically locks in place with assistance from the side push buttons For Best Use: avoid using this accessory for edging, working alongside brick, chain, or wooden fencing Products Include: The package contains 8 Pack Polycarbonate Blades and 4 Set Screw, 1 Pack Trimmer Head,1 Pack Tool wrench After-Sales Assurance: Pls contact us first when you get some problem, we will offer you assistance asap THTEN SF-080 Trimmer Blades Head Compatible with Black & Decker GH3000 LST540 GH3000R LST540B Edger Grass Trimmers 18 Pack