Proto J5521M 21mm 3/4 Drive 12-point Hand Socket

Product Description

The PROTO J5521M is a 21 mm, 12-point hand socket designed for heavy-duty fastener work in professional tool kits. Built on a 3/4-inch drive, it delivers the torque capacity needed for large fasteners encountered in industrial, mechanical, and fleet maintenance applications. The 12-point geometry allows engagement from multiple positions, reducing the need to reposition the socket in tight spaces. A chrome-plated finish resists corrosion and makes the socket easy to clean after use. Standard length design fits the majority of service situations without the clearance complications of deep-well sockets. This socket is intended for use by mechanics, millwrights, and other trades professionals who regularly work with large-diameter fasteners.

The PROTO J5521M suits applications requiring a 3/4-inch drive in automotive, heavy equipment, industrial machinery, and structural assembly environments. It is sized for M21 metric fasteners common on drivetrain components, suspension hardware, and industrial equipment mounting hardware. Standard length makes it compatible with most 3/4-inch drive ratchets, breaker bars, and torque wrenches available in professional tool inventories.

Key Features

• 21 mm socket size for metric fastener applications
• 3/4-inch drive for high-torque service work
• 12-point design allows multiple engagement positions on fastener heads
• Standard length profile fits most 3/4-inch drive handles and extensions
• Chrome-plated finish provides corrosion resistance and easy cleaning

Compatibility

Designed as a standard-fitment 3/4-inch drive hand socket compatible with 3/4-inch drive ratchets, breaker bars, torque wrenches, and extension bars from professional tool systems.

Installation Notes

Installation and removal of fasteners should be performed by qualified mechanics or trades professionals familiar with proper torque procedures. Ensure the socket is fully seated on the fastener before applying force to prevent rounding. Inspect the socket for cracks or wear before each use, and do not use damaged sockets. Impact-rated sockets should be used in place of hand sockets when impact wrenches are required.