16 mm inside and on-the-tread clearance. Manual tensioning system: one stop to fit the chain and one to tighten it. Closed shortening hooks avoid coils on the chain. Homologations/certifications/conformity: ?-Norm 5117, ?-Norm 5119, UNI 11313 / CUNA, TüV. Snow chain size: 31/11.50 - 15, 235/85 - 16, 265/70 - 16, 265/65 - 17, 275/60 - 17, 255/60 - 18, 265/60 - 18, 255/55 - 19, 265/50 - 19, 285/45 - 19, 255/50 - 20, 275/45 - 20, 295/40 - 20, 315/35 - 20, 265/40 - 21, 265/45 - 21, 295/35 - 21