Wrench Size: 13/16 inch. Tool Type: Combination open-end socket wrench. Lobular Design: Incorporates an advanced internal profile that exerts turning force directly on the flat sides of the fasteners rather than the corners. This critical feature provides better torque, prevents fastener rounding, and helps spin out even badly worn or rusted hardware. Build Quality: Constructed from premium tool steel that was custom heat-treated by Armstrong to achieve optimal hardness and "spring" flexibility under heavy loads. Precision Openings: Features precision broached openings to ensure a secure, exact fit over fractional SAE fasteners.