Huhuhero Portable Automatic Quick Electric Pencil Sharpener with One Extra Replacement Sharpener Core, Battery or USB Powered (Yellow) Automatic safety lock function - The pencil sharpener stops operation when the shaving tray is removed; safe to use Never over-sharpening - The sharpener will idle automatically once the pencil tip has been shaved within 0.3 - 0.5 mm (0.01 inch-0.02 inch) Replaceable Sharpener Core Design - Greatly extending the sharpening service life. ( 1 x replacement core included ) Fast and stable to use - Sharp & durable SK5 steel blade with fast cleaning and stable cutting performance Multiple Power Sources - Can be powered by either USB cord (inlcuded) or 4 AA batteries (not included). NOTE: SINCE THE VOLTAGE INSTABILITY WILL CAUSE THE SHARPENER DOES NOT WORK, PLEASE TRY DIFFERENT USB PORT OF NOTEBOOK