Metric Short Arm Allen Keys/ Hex Wrench/ Hexagon Key 1.5mm to 14mm Nickel Plated

On a standard L-shape hex key, the short arm is the shorter leg and the long arm is the longer leg. Using the short arm as the driver gives you more torque with less rotation, which is useful for breaking loose tight fasteners. Using the long arm as the driver gives you faster rotation with less torque, useful for running down a fastener quickly. A short arm Allen key specifically refers to a key where the overall working-end length is reduced, making the tool more compact and easier to use in confined spaces.

The correct size matches the hex socket in your fastener. Common pairings: M3 keys for bicycle brake cable pinch bolts, M4 for furniture cam bolts, M5 for stem and handlebar bolts, M6 for most machinery set screws, M8–M10 for larger structural hex socket bolts. If unsure, measure the width across the flats of the hex socket with a caliper — that measurement in millimeters is your key size.

These keys are machined from carbon steel, which provides adequate torsional strength for the torque specifications of standard metric hex socket fasteners in their respective size range. For very high-torque industrial applications (e.g., structural bolting beyond M10), a torque wrench with a hex bit socket is generally recommended over any L-key to avoid overloading the tool.

The nickel-plated finish provides a barrier against light moisture and surface oxidation, making these keys more corrosion-resistant than bare carbon steel. For prolonged exposure to water, salt spray, or harsh chemicals, wipe the keys dry after use and store them in a dry location. The plating is not a substitute for stainless steel in continuously wet environments.

Metric and imperial hex sizes are not interchangeable. Using a metric key on an SAE fastener (or vice versa) risks rounding the socket corners. Always match the key standard to the fastener standard. These keys are metric only (M1.5–M14). If you need SAE sizes, please check our other listings.

If you need a specific replacement size for a known fastener, a 1- or 2-piece pack is the most cost-effective option. If you are stocking a toolbox, workshop, or job site where multiple sizes will be used regularly, the 5-, 10-, 20-, or 50-piece packs offer a lower per-unit cost. The 50-piece pack is particularly suited for trade use or situations where keys are frequently misplaced or shared among multiple users.

The M-number (e.g., M3, M6) refers to the nominal hex key size in millimeters — specifically the width across flats of the hexagonal cross-section. This corresponds directly to the hex socket size of the fastener the key is designed to drive. An M5 Allen key fits an M5 hex socket, which is typically found on M5 socket head cap screws (though the fastener thread diameter and the key size are separate dimensions).