Adjustable flat wrench Wera JOKER 16–19 mm, self-adjusting open-end spanner

The Wera JOKER adjustable flat wrench with a 16–19 mm self-adjusting open-end jaw is a compact hand tool designed to grip and turn bolts and nuts within the specified size range without changing tools. Its flat, low-profile design reduces interference in confined areas while the self-adjusting jaw adapts quickly to the fastener width. The tool is intended for mechanical, maintenance and assembly work where accessibility and speed are important.

Advantages

The self-adjusting jaw automatically adapts to bolt and nut widths from 16 to 19 mm, saving time that would otherwise be spent swapping spanners. The flat profile allows access in narrow spaces and reduces the risk of knocking adjacent components. Durable construction and precision-machined jaw faces ensure a secure grip and consistent force transfer. The tool's compact size makes it convenient for both workshop and field use, offering an efficient alternative to multiple fixed-size open-end wrenches.

Suitable for

• Automotive and motorcycle maintenance where access is limited
• Assembly and disassembly of machinery with fasteners from 16 to 19 mm
• On-site service and repair tasks requiring a compact, adaptable wrench
• General mechanical and maintenance work in workshops and production lines

Key specifications

• Adjustable jaw range: 16–19 mm
• Open-end, flat wrench profile for low-clearance access
• Self-adjusting mechanism for rapid adaptation to fastener width
• Material: hardened steel construction for durability (manufacturer standard)
• Suitable for right- and left-hand fastening operations
• Compact length and slim cross-section for tight spaces

How to use

Place the wrench over the bolt or nut so the self-adjusting open jaw contacts opposing faces of the fastener. Apply steady pressure to maintain engagement and turn the wrench in the required direction. The spring-assisted jaw will conform to the fastener width within the 16–19 mm range; no manual size adjustment is needed. For loosening seized fasteners, apply controlled force and ensure the wrench is correctly seated to minimize slippage or rounding of the fastener corners.

Usage recommendations

Inspect the fastener and the wrench jaw faces before use to ensure clean contact. Use the wrench only within its specified jaw range (16–19 mm) and avoid excessive torque beyond typical hand-tool limits. Store the tool in a dry place and keep jaw surfaces free of debris to maintain reliable self-adjusting function.