U1, U2, U3, U4 Grades. The more the Grade number, the more the Tensile Strength. Considering Standards, diameters are between  (12.5mm) to  (137mm). In another word, MBL is between 13.5 MT to 174 MT.

Length measurement unit is foot and one length unit is equal to 90 ft = 27.5 m.

In general, these types of chains are High Carbon colorless (self-color) or hot deep galvanized and the second type provide more resistance against the salts.