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SAE MA 1586A-1987 (SAE MA1586A-1987)
Wrench Configuration, 12 Spline Drive, Metric ( Reaffirmed: Feb 1992 )
Tools conforming to this standard will wrench fasteners having wrenching configurations per MA 1549. Nominal wrenching size value corresponds to maximum width across flats of comparable hexagon and double hexagon (12 Point) wrenching configurations. The wrench will fit all three configurations.
Society of Automotive Engineers [sae]