Features and Benefits:

• Forged from the finest chrome-molybdenum alloy steel, the best choice for strength
• Radius corner design extends the life of fasteners, design drives the side of the fastener instead of the corner
• Design also avoids rounding of rusted or damaged fasteners
• Black oxide finish and has etchings for identification

This is an impact socket and it is 21mm. It is 1 in. drive and double square design. Designed to tackle the toughest jobs with solid durability and keeps them pounding job after job.