Sunex 3358, 3/8 Inch Drive Metric Standard Impact Socket Set, 13 Pieces, 7mm to 19mm, Cr-Mo Alloy Steel, Radius Corner Design, Dual Size Markings, Heavy Duty Storage Case Included CR-MO ALLOY STEEL: Increases impact socket strength and durability. RADIUS CORNER DESIGN: Allows for better grip on fasteners and reduces fastener wear over time. INCREASED TORQUE STRENGTH: A combination of Cr-Mo steel and our radius corner design. DUAL SIZE MARKINGS: Laser etched and roll stamped markings to ensure permanent socket identification. HEAVY DUTY STORAGE CASE: Convenient impact socket transport and storage. 13 PIECES SET METRIC: 7mm to 19mm