The Carbide ER-11 Compact Router is a custom-made trim router packaged for use with any Shapeoko CNC routers. Why buy an ER-11 router? There's only one reason to buy this router over the less expensive Carbide Compact Router: you need to use cutters or drills with a shank diameter other than 1/8" and 1/4". Other than the collets, there is no difference. The ER-11 Compact Router was made for use in CNC machines so we skip all of the bases and jigs that won't be used anyway.