A 5.5 mm combination spanner is a hand spanner with an open jaw at one end and a ring (box) end at the other, designed specifically to fit 5.5 mm metric nuts and bolts. Its primary use is for tightening and loosening small metric fasteners where access or grip from two different end styles is required, commonly in light engineering, maintenance and precision assembly work.

This spanner is manufactured from chrome‑vanadium (Cr‑V) alloy steel and is heat treated to provide the torsional strength and fatigue resistance required for repeated workshop use. The tool is supplied with a bright chrome plated, polished finish to resist corrosion and to ease cleaning of oil and dirt from the surface. The head configuration is combination style: one open jaw for quick engagement and a 12‑point ring (box) end for improved contact with bolt heads in confined spaces. The span and manufacturing tolerances conform to recognised DIN/ISO/BS dimensional standards for hand spanners to ensure accurate fit on metric fasteners.

Typical applications for a 5.5 mm combination spanner include electronics and instrumentation assembly, small appliance repair, bicycle and motorcycle maintenance, HVAC controls and general workshop or site maintenance where small metric fixings are used. The small size makes it especially suited to working in tight spaces and on delicate assemblies where larger tools would be inappropriate.

Key benefits of this spanner are its corrosion resistance from chrome plating, the strength and longevity afforded by chrome‑vanadium construction and heat treatment, and the accurate, standardised sizing that reduces fastener rounding and slippage. The dual‑ended design improves versatility, enabling quicker workflow by switching between open and ring ends without changing tools. The tool is compatible with standard ISO metric fasteners and will sit alongside other metric spanners in mixed toolkits.

Duchy Fasteners stocks this 5.5 mm combination spanner individually and in assorted metric sets; additional metric sizes and pack quantities are available on request to suit professional and trade requirements.