1.5-32mm Allen Keys Hexagon Key Hex Wrench Extra Long 4mm 5mm 6mm 8mm 10mm 14mm

Measure the width across the flats of the hex socket in your bolt or screw using a caliper or ruler. The measurement in millimeters corresponds directly to the Allen key size you need. For example, a socket measuring 4mm across the flats requires a 4mm hex key. When in doubt, start with a slightly smaller key and work up — a loose fit will damage both the key and the fastener.

The extended long arm gives you two advantages: greater reach into deep or recessed bolt holes, and increased mechanical leverage so you can apply more torque with less effort. The short arm is still available for fast spinning in open areas. This makes extra-long hex keys particularly useful for furniture assembly, bicycle maintenance, and machinery work where fasteners are often set deep into frames or housings.

These wrenches are machined from hardened alloy steel, which provides good resistance to twisting and rounding under typical DIY and light industrial torque loads. For very high-torque industrial applications (e.g., large structural bolts), a torque wrench with a hex bit socket is generally recommended for controlled tightening. Always apply force gradually and avoid using extension pipes on the handle, which can exceed the wrench's rated strength.

The black oxide finish provides a degree of corrosion resistance for workshop and occasional outdoor use. For prolonged exposure to moisture, wipe the wrenches dry after use and apply a light coat of machine oil to the surface. Black oxide is not equivalent to stainless steel or zinc plating — it is a surface treatment that slows, but does not fully prevent, rust in continuously wet conditions.

Most flat-pack furniture uses metric hex socket bolts in sizes ranging from 3mm to 8mm. The 3mm, 4mm, 5mm, 6mm, and 8mm variants in this range are directly compatible with the majority of IKEA and similar flat-pack hardware. Check your furniture's assembly instructions for the specific hex size required before selecting a variant.

Smaller sizes (1.5mm–3mm) are sold in packs of 5 because they are more prone to misplacement and occasional bending under misuse — having spares on hand is practical. Larger sizes (4mm and above) are sold in smaller quantities (1–2 pcs) because they are used less frequently and are less likely to be lost. If you regularly work on bikes or machinery, consider ordering an extra unit of your most-used size.