From the Manufacturer
Professional router bit extension for 1/2-Inch collet routers.
The single tool cutter changing eliminates searching for and holding the spindle lock while securing the collet with a wrench. Use the included 1/4″ x 1/2″ reduction sleeve to safely support your 1/4″ shank cutters. NOTE: A 1-3/4″ hole is required in the insert or table to allow the body of the extension to pass through for above table cutter changes.
