Package Include:1 Trimmer Head Replacement Part NO.:55-491 Dimensions:M10x1.25LHF Designed for professinal landscapers,fits Most of all straight shaft gas trimmers such as Echo,Green machine,Hom-lite,Hus,John-D,Poulan,Red-max, Ryobi,Shin-daiwa,Sthil,Weed eater and others. Please confirm the models and dimensions before purchasing,thank you. Package Include:1*Trimmer Head