SHIMANO HG51 8-Speed Cassette Review Posted on August 3, 2018November 9, 2018 By ArchSeaLionPosted in Drivetrain ComponentsTagged Cycling, Outdoor Recreation, Parts & Components, SHIMANO, Sports & Outdoors 8-Speed Precise and consistent HyperGlide shifting performance. Long leg spacer for further weight reduction. Enlarged sprocket window design for lighter weight.