A ring spanner surrounds the nut and grips all six flats, which is why it is the spanner used to break a fastener loose and to make the final tighten. Nothing on the leaf grips harder, and a nut that will round under an open spanner comes free under a ring. A ring also drives the nut evenly, so the load is spread rather than concentrated on two corners.
The limitation is access. A ring has to drop over the nut from above, so it cannot be used on a pipe union, a captive fastener or anything with something above it. That is what the open ended and flare nut spanners on the adjacent leaves exist for.
Offset is what lifts the knuckles clear of the work. A flat ring spanner sits in the same plane as the handle, which suits an open fastener. A deep crank offsets the ring below the handle so a nut set below a face can be reached without the hand fouling it. Both patterns are held across the size range rather than the offset being fixed by size.
Sizes are quoted in pairs with both ends differing, from 7 x 8mm and 8 x 9mm through 14 x 15mm, 16 x 17mm and 18 x 19mm to 27 x 32mm. Offset depth is stated per spanner rather than being uniform. Measure the nut across the flats and send the figure to 07754288583 on WhatsApp with a photo of where it sits.
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