M2~M8 Metric Short Arm Allen Keys Hex Wrenches Hexagonal Key 0.9mm~4mm All Sizes

Match the hex key size to the socket opening of your screw, not the thread diameter. For example, an M4 socket head cap screw typically uses a 3 mm hex key (M4 key in this listing). If you are unsure, measure the width across the flat faces of the socket opening with a caliper. The key should seat fully with no play before you apply torque.

A short arm hex key has a compact working end, making it easier to fit into recessed cavities, tight enclosures, and furniture hardware channels. A long arm key provides more torque leverage but requires more clearance to rotate. Short arm keys are preferred when space is limited; long arm keys are preferred when maximum torque is needed on a fastener that is accessible from above.

Yes. The keys are manufactured from hardened alloy steel, which provides sufficient torsional strength for standard metric socket head cap screws and grub screws in M2–M8 sizes. Avoid applying excessive force beyond the rated torque for the fastener size, as over-torquing can round the socket regardless of key material.

Black oxide provides light corrosion resistance suitable for dry indoor environments. For outdoor or high-humidity applications, wipe the keys with a light machine oil after use and store them in a dry location. If you need keys for consistently wet or corrosive environments, consider stainless steel alternatives.

These are traditional L-shaped short arm hex keys designed for direct hand use. They are not designed to be inserted into a T-handle or power tool bit holder. If you need a hex bit for use with a driver, look for hex insert bits sized to match your fastener.

The hex key variants (M2–M8 and Hex Wrench options) are the driving tools — the L-shaped keys you use to tighten or loosen fasteners. The set screw variants (M2×2 through M8×8 Screw options) are the actual fasteners — small headless screws driven by a hex key. If you need both the screw and the tool to drive it, you can select each from the Key Size dropdown on this page.

For a general workshop, a set of 1–5 pieces per size is typically sufficient for maintenance tasks. For production environments where keys are shared across workstations or subject to frequent use, ordering 20–50 pieces per size reduces downtime from lost or worn tools. The bulk quantity options (up to 500 pcs for set screws) are suited for assembly line restocking.