Metric Allen Key-Hex Wrench M0.7/0.9/1.2/1.5/2/3/4/5/6/8/10/12 Black/Ni-plated

Measure the width across the flats of the hex socket in your fastener using a caliper or a reference gauge. The measurement in millimeters corresponds directly to the key size — for example, a 3 mm socket requires a 3.0 mm hex key. If you are unsure, start with the next size down and work up; a key that fits snugly with no wobble is the correct size.

Black Carbon Steel keys are treated with a black oxide finish that provides basic corrosion resistance and a non-reflective surface. They are well-suited for indoor, dry workshop use. Ni-plating CRV (Chrome Vanadium) Steel keys have a nickel-plated surface that offers greater corrosion resistance and a harder exterior, making them a better choice for humid environments, outdoor maintenance, or applications where the tool will be exposed to moisture or mild chemicals.

No. These are metric hex keys designed for metric hex socket fasteners only. SAE hex fasteners use inch-based sizing (e.g., 1/8 in, 3/16 in) which does not correspond directly to metric millimeter sizes. Using a metric key in an SAE socket — or vice versa — risks rounding out the fastener head. Please verify your fastener's measurement system before ordering.

The long arm of an L-shape hex key provides greater torque leverage, which is useful for loosening stubborn fasteners or driving screws into harder materials. However, applying excessive torque — especially on smaller sizes such as 0.7 mm to 2.0 mm — can twist or snap the key. For very high-torque needs on small fasteners, use controlled, steady pressure rather than sudden force, and consider using a T-handle or bit adapter for better control.

If you already own most sizes and only need to replace a specific worn or lost key, ordering individual pieces (1, 2, or 5 pcs) is the most cost-effective option. If you are building a new tool kit or need coverage across a broad size range, the kit options — 0.7–8.0 mm in Black Carbon Steel or 1.5–12 mm in Ni-plating CRV Steel — provide a complete set in a single order and typically offer better value per piece.

After use, wipe the keys clean with a dry cloth to remove metal filings, grease, or moisture. For Carbon Steel keys, applying a light coat of machine oil periodically helps prevent surface rust. Store keys in a dry location — a roll pouch, magnetic holder, or indexed rack keeps sizes organized and prevents the tips from contacting hard surfaces that could chip the hex profile. Inspect the hex ends regularly; a key with a visibly worn or rounded tip should be replaced to avoid damaging fastener heads.

For a professional or high-frequency workshop setting, ordering in quantities of 5 pcs per size ensures you have spares on hand when a key is misplaced or worn. The 5-pcs packing option also reduces the per-unit cost compared to single-piece orders. For sizes used most frequently in your work — typically M3, M4, M5, and M6 in general mechanical assembly — stocking a higher quantity is advisable to avoid workflow interruptions.