Wolverine 1″ Knot Wire End Brush features hollow end construction and heavy duty brushing action. Ideal for more demanding cleaning applications in recessed areas. 1/4″ stem diameter for use on die grinder, drill and drill presses. Hollow end construction and heavy duty brushing action. For cleaning heavy deposits from valve guides in gas and diesel engines. 2000 rpm maximum speed. Ideal for more demanding cleaning applications in recessed areas. .