Proto J4990-5MST Hand Hex Bit Socket 3/8 in 5mm

Product Description

The PROTO J4990-5MST is a hand hex bit socket designed for 3/8 inch drive tools and 5 mm hex fasteners. It delivers a direct, positive fit on internal hex fasteners commonly found in mechanical assemblies, HVAC equipment panels, electrical enclosures, and plumbing fixture components. The overall length is 1-49/64 inches with a bit length of 3/4 inches, making it compact and suited for work in confined spaces. Trade professionals reach for this socket when driving or breaking loose metric hex bolts and cap screws in tight quarters where a standard Allen key lacks the torque leverage of a ratchet-driven socket.

This hex bit socket fits standard 3/8 inch drive ratchets, torque wrenches, and extension bars. It is well suited for residential and light commercial service work where metric hardware is common, including equipment mounting hardware, valve packing nuts, panel fasteners, and machinery set screws. HVAC technicians, plumbers, electricians, and mechanical service pros keep this size on hand for general metric fastener work across a wide range of service calls.

Key Features

• 3/8 inch drive accepts standard ratchets, extensions, and torque wrenches
• 5 mm hex bit size for metric internal hex fasteners
• Compact 1-49/64 inch overall length suits tight installation spaces
• 3/4 inch bit length provides adequate engagement depth on standard hex fasteners
• Bit socket design converts a ratchet drive into direct hex drive without a separate adapter

Compatibility

Designed as a direct-fit 3/8 inch drive hex bit socket compatible with standard 3/8 inch drive ratchets, extensions, and torque wrenches. Intended for use on 5 mm internal hex fasteners.

Installation Notes

Installation and removal of fasteners with this socket should be performed by a qualified tradesperson familiar with proper torque requirements for the fasteners being driven. Ensure the socket is fully seated on the drive tool and fully engaged in the hex recess before applying torque to prevent rounding of the fastener. Do not use impact drivers unless the socket is rated for impact use.