1. A Ring Spanner is a spanner in which the jaws form a ring with internal serrations which fit completely around a nut, usable in confined spaces.

2. A ring spanner is a simple, double-headed, single-piece spanner with a profile set in a looped head.

3. The loop is placed over the head of the fastener and the spanners profile pushes against the flat sides of the fastener head to turn it. 

4. As it grips all the sides it does not slip.

5. They can be turned in wider arcs more easily, making the task quicker.