Combination wrench Unior U600371 20 mm, open-end and box-end hand tool

The Unior combination wrench U600371 20 mm is a single-size hand tool with an open-end on one side and a box (ring) end on the other. Designed for tasks that require a precise 20 mm fit, the wrench provides two common engagement options for fastening and loosening hexagonal nuts and bolts. Manufactured by Unior, this combination spanner is intended for bicycle maintenance, automotive repairs and general workshop or household use where consistent torque and access to confined fasteners are needed.

Advantages

The tool combines the speed and accessibility of an open-end with the secure engagement of a box-end, reducing rounding of fasteners and improving control during turning. Its single-size format simplifies tool selection when a 20 mm fastener is present and lowers the weight and bulk compared with multi-piece sets. The box-end offers multiple contact points for even torque distribution, while the open-end allows work on fittings with limited clearance or partially obstructed fasteners.

Suitable for

• Bicycle repairs and component adjustments that require a 20 mm spanner
• Automotive maintenance tasks such as brake caliper, suspension or body fasteners sized 20 mm
• Workshop and garage use for assembly, disassembly and routine maintenance
• Household plumbing or mechanical jobs where a reliable 20 mm wrench is needed

When it may not be suitable

This single-size combination wrench is not a substitute for a full metric set when you face fasteners of various sizes; frequent work on different diameters will require additional spanners. Also, for very high torque applications or impact work, a dedicated torque wrench or impact-rated tools are more appropriate, as standard hand spanners are not designed for impact loads.

Key specifications

• Size: 20 mm across flats
• Type: Combination wrench with open-end and box-end
• Material: heat-treated alloy steel (typical for hand spanners)
• Drive/contact: 6- or 12-point box engagement depending on model design
• Finish: corrosion-resistant surface treatment (chrome or similar plating)

How to use

Select the box-end for maximum contact and reduced risk of rounding when the fastener is accessible and there is room for the wrench to engage fully. Use the open-end side for fasteners in tighter spaces or where the fastener must be approached from the side. Position the wrench so that force is applied along the handle axis and pull rather than push when possible to reduce the chance of slippage. Inspect the fastener and wrench for wear before use and avoid using the wrench on rounded or damaged heads.

What to consider before purchase

• Confirm that the fasteners you will work on are 20 mm in size
• Consider whether you need a single spanner or a full set for broader coverage
• Check compatibility with tight access points and the orientation of the box-end/reach
• Decide if corrosion-resistant finish or specific material hardness is required for your environment

Usage recommendations

Use the box-end for initial loosening or final tightening where full engagement is possible, and switch to the open-end for quick adjustments or when space is restricted. Store the wrench in a dry toolbox or hang it on a rack to maintain the finish and check regularly for straightness and wear before applying high torque.