A wrench extender not only lets you apply greater torque when loosening a tight nut, but it keeps your hands clear of the teeth on a saw blade when installing or removing one.
With a router, where you often have wrenches that are too short to let you apply enough torque (particularly if you are using collets in the chuck), they are a necessity.
If the router is mounted to a router table, extenders will also let you work without exposing your knuckles to the router clamps, useful whether you need the extra torque or not.
The compact size (9" x 2" x 3/8") makes access easy, and the length still allows you double or triple the amount of torque you could apply without it.
All-steel construction, zinc plated with a synthetic rubber handgrip. Fits wrenches up to 1/4" thick and 1-1/4" wide.