Allen Ball End Hex Key Wrench 1.5mm 2mm 2.5mm 3mm 4mm 5mm 6mm 8mm 10mm 12mm 14mm

The ball-end tip on the long arm allows the wrench to engage a fastener at an angle — typically up to about 25–30° off-axis — so you can drive screws in confined spaces without needing a straight approach. The short arm has a standard flat hex tip that provides full surface contact for maximum torque when you need to apply extra force to break loose or fully seat a fastener.

Most road and mountain bike stem bolts use 4 mm or 5 mm hex keys. Derailleur limit and cable-pinch screws are typically 2 mm or 2.5 mm. Brake caliper mounting bolts often require 5 mm or 6 mm. Check your component manufacturer's specification if you are unsure — the size is usually stamped on the bolt head or listed in the component manual.

Chrome-vanadium (Cr-V) steel is a standard alloy for hand tools because it combines good tensile strength with toughness, meaning it resists both bending and sudden impact. For typical DIY and light-to-medium professional use — furniture assembly, bicycle maintenance, and general machinery adjustment — Cr-V hex keys are well-suited. For very high-torque industrial fastening, always use the short arm (standard hex end) rather than the ball end, which is designed for access, not maximum torque.

Black oxide provides mild corrosion resistance by converting the surface iron into a thin magnetite layer. It is suitable for dry indoor workshop environments. For prolonged outdoor exposure or humid conditions, wiping the wrench with a light machine oil after use will extend its service life. Black oxide is not a substitute for stainless steel or heavy plating in corrosive environments.

These wrenches are metric sizes only (1.5 mm–14 mm). Metric and imperial hex sizes are not interchangeable — using a metric key on an imperial fastener (or vice versa) risks rounding the socket. If you work with both metric and SAE fasteners, you will need a separate imperial (inch) hex key set.

Flat-pack furniture most commonly uses 4 mm and 5 mm hex bolts for structural joints, and 3 mm for smaller fittings. The required size is usually shown in the assembly instructions or printed on the hardware bag. If you are replacing a lost key, measure the bolt socket width across flats with a caliper — that measurement equals the hex key size you need.

Each listing is for one individual wrench. Select the specific size you need from the size options above. This lets you replace a single worn or lost key without purchasing a full set, or stock up on the sizes you use most frequently.