Hex key Proline 4 mm — Proline 48522, single metric Allen key

Proline 4 mm hex key (Allen key) is a single metric hand tool designed for driving screws with a 4 mm hexagonal socket. The compact, straight L-shaped tool provides a precise fit for 4 mm fasteners and is intended for routine assembly, maintenance and repair tasks in workshops and around the home. Its simple construction ensures reliable torque transfer and controlled handling when tightening or loosening hex bolts.

Advantages

The solid steel construction and accurately machined tip provide a snug engagement with 4 mm hex sockets, reducing wear on both tool and fastener. Its compact length makes it easy to carry in a toolbox or pocket and convenient for use in confined spaces. The long arm gives additional leverage when higher torque is required, while the short arm allows quick turning in tight areas. The straightforward design requires no additional adjustments or accessories.

Suitable for (tasks / use cases)

• Assembling and tightening furniture fasteners with 4 mm hex heads
• Bicycle maintenance where 4 mm Allen keys are specified
• Small machinery and equipment servicing that uses 4 mm hex screws
• General household repairs involving 4 mm hex bolts

Key specifications

• Tip size: 4 mm hex
• Tool type: single metric hex (Allen) key
• Shape: L-shaped (short and long arm)
• Material: hardened steel (solid construction for torque transfer)
• Finish: corrosion-resistant surface treatment

How to use

Select the 4 mm end and insert it fully into the hex socket of the fastener to ensure correct engagement. Use the short arm for rapid turning and the long arm to apply greater torque when loosening or tightening. Maintain a straight alignment between the key and the fastener to avoid rounding the socket. After use, wipe the tool clean and store it in a dry place to preserve the surface treatment and prevent corrosion.

Usage recommendations

Use only the exact 4 mm hex key for 4 mm fasteners to avoid damaging screw heads. Do not use cheater bars or excessive force beyond typical hand torque; for high-torque applications, consider a dedicated tool designed for greater leverage or impact drivers specified for hex fasteners.