3/8-inch Metric Socket Set

The 3/8-drive size is the bike-shop workhorse for fasteners that sit above the 1/4-drive ceiling but below the 1/2-drive heavy-torque range. Pedal-axle nuts (15 mm flats), older crank-arm bolts (14 to 17 mm flats), axle nuts on solid-axle wheels, and most cassette-adjacent fasteners live in the 7–22 mm window this set covers.

Sixteen 6-point sockets on a clip rail, sized from 7 to 22 mm. The right choice when you've outgrown a 1/4-drive set's torque ceiling and need real sockets for serious work.

What's in the set

Sixteen 6-point metric sockets:

• 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 mm

The 6-point geometry is the right choice for bike work. A 6-point socket contacts the fastener flats squarely; a 12-point socket contacts at corners and can round flats on softer alloy nuts. Modern bike fasteners are mostly aluminum or titanium alloy, which means corner-contact is a slow-rounding problem you don't want to inherit.

Where the 3/8-drive sizes land in bike work

• 15 mm: pedal-axle nuts (standard on modern pedals)
• 14 mm: common older crank-arm bolt size
• 17 mm: axle nuts on solid-axle commuter wheels; some BB lockrings
• 22 mm: larger external-hex BB lockrings; some headset top caps
• 10–13 mm: medium-torque fasteners across the rest of the bike

For higher-torque jobs (cassette lockring at 40 Nm, crank-arm bolt at 50 Nm) you may still want a 1/2-drive socket and ratchet; the 3/8-drive square will twist under 50 Nm of sustained load. Use 3/8 for the 10–35 Nm range; use 1/2 above that.

Specs

• Drive size: 3/8 inch
• Socket count: 16 metric
• Socket profile: 6-point
• Socket range: 7 mm to 22 mm
• Storage: clip rail
• Construction: chrome-vanadium steel, hardened and tempered

Made in Slovenia, since 1919

Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. The 6-point geometry is the deliberate choice across our socket line; we sell 12-point patterns in specific positions where the geometry earns its place, but our default for bike work is 6-point because the failure mode of 12-point on alloy nuts is well-documented. Choosing the geometry that matches the workpiece is the same kind of decision the brand has been making since the cycling-tools line started.

Pro tip from our mechanics

If you only own one drive size, 3/8 is the most versatile for bike work. The 1/4-drive sees more cycle counts on small fasteners, but the 3/8-drive is where most of the meaningful torque happens. For the framework on which drive size belongs where: Sockets and bits for bike work →.