Hex Key (Allen) Bondhus 4.0 mm — Long Arm 110 mm, Model BO13960

Bondhus 4.0 mm hex key (Allen) with a long arm of 110 mm, model BO13960, is a steel hand tool designed for driving 4.0 mm hex fasteners. The extended long arm provides reach into recessed or deep-set screw heads while maintaining a compact short arm for controlled torque. Intended for maintenance, assembly and repair tasks, this hex key offers a consistent fit with hex sockets to reduce rounding and slippage.

Advantages

The long arm length of 110 mm improves access to fasteners located in deep or hard-to-reach areas without requiring extensions or adapters. Precision-machined hex profiles ensure a snug fit in 4.0 mm hex sockets, lowering the risk of cam-out and screw damage. Made from heat-treated steel, the key resists wear under repeated use and provides reliable torque transfer. The simple straight design enables both high-torque short-arm use and reach-focused long-arm leverage.

Suitable for

• Maintenance and repair of machinery with recessed hex fasteners
• Assembly of metal or plastic components requiring a 4.0 mm hex driver
• Electronics and appliance servicing where longer reach is needed
• DIY projects and professional workshops that require precise hex torque control

Key specifications

• Hex size: 4.0 mm
• Long arm length: 110 mm
• Material: heat-treated steel
• Drive type: straight long-arm hex (Allen) key

How to use

Select the 4.0 mm hex key and insert the short or long arm into the screw head depending on the required torque and reach. Use the short arm for higher torque turning and the long arm for accessing recessed fasteners or applying controlled light torque. Ensure the key is fully seated in the hex socket before turning to minimize slippage. Apply steady pressure and turn clockwise to tighten or counterclockwise to loosen. After use, wipe clean and store in a holder or toolbox to protect the hex profile.

Usage recommendations

For best results, confirm the 4.0 mm size matches the fastener to avoid rounding. Avoid excessive force that exceeds the material strength of fasteners; when higher torque is needed, consider using the short arm or a torque-limiting tool. Keep the hex key dry and free of grit to prolong service life.