Standard Series -- (HTM - - - Series) Made in a range of stock sizes for convenient adjustment around standard diameters (typically in OEM or other production assembly work). Liner Series -- (HTM - - - L Series) Identical with HTM series except that the single-piece band is extended underneath the adjustment slots to protect silicone or other soft-surface materials. Multiples Sizes (HP - - - Series) This special series of Hi-Torque clamps offers a greatly expanded working diameter range by adding extra perforations to the band: eg. HP 4 covers working diameters normally covered by HTM-500, HTM-550 and HTM-600. Only 4 sizes covers working diameters from 1-1/4" (32 mm) to 9-1/8" (232 mm).