Proto J5221MH 21mm 6-point 3/8 Drive Hand Socket

Product Description

The PROTO J5221MH is a 21 mm, 6-point hand socket designed for 3/8 inch drive ratchets and breaker bars. Chrome-plated and built to standard length, it delivers solid contact on hex fasteners in a wide range of mechanical and maintenance applications. The 6-point geometry reduces the risk of rounding fastener corners compared to 12-point designs, making it a reliable choice when working with tight or corroded hardware. Meets ASME B107.5 standards and carries a lifetime warranty. Suited for professional mechanics, industrial maintenance techs, and trade pros who need a dependable impact-ready socket in common metric sizing.

This socket fits into general mechanical service work including automotive, HVAC equipment fasteners, plumbing fixture hardware, and light industrial maintenance. Its standard length profile works well in open or moderately confined spaces where a deep socket is not required. The chrome finish resists corrosion and makes it easy to wipe clean between uses. Sold individually, making it a straightforward replacement or addition to an existing 3/8 inch drive socket set.

Key Features

• 21 mm socket size fits common metric fasteners in automotive and mechanical applications
• 6-point contact geometry reduces fastener rounding on stubborn or corroded hardware
• 3/8 inch drive compatible with standard ratchets, extensions, and breaker bars
• Chrome-plated finish resists corrosion and simplifies cleaning
• Standard length profile suits open and semi-confined workspaces
• Meets ASME B107.5 standards with a lifetime warranty

Compatibility

Designed for use with 3/8 inch drive ratchets, extensions, and torque wrenches. Fits 21 mm hex fasteners in standard mechanical and maintenance applications.

Installation Notes

Used by mechanics, HVAC technicians, plumbers, and general maintenance professionals. Ensure the drive tool and socket are fully engaged before applying torque to avoid slippage. Inspect the socket for cracks or wear before use, particularly when working with high-torque fasteners. Do not use hand sockets with impact drivers unless the socket is rated for impact use.