The Master Grade has been designed for very simple operation that will allow the skilled craftsman as well as a complete novice to obtain razor sharp results and also save time. The precise guides ensures that the knife will be sharpened at the correct angle for razor sharp results. Works for most knives, including serrated knives.It is not for single edge or negative curve knives It is able to create knife''s angle from 6 to 32 degree angle. If you want to create a new angle, just press harder. Please refer to user manual for details, otherwise, this machine Automatically adjusts angles to match your knives'' angles. It comes with narrow opening top, guided 15 degree angle Used unique "soft touch" and flexible sharpening wheels No water or oil, no mess during sharpening Built with fire resistance housing Safe and durable, easy to maintain, just clean it regularly Easy to use, save time and money UL commercial and NSF certifications Size L X W X H : 13" x 4.9" x 4.5"