SharpTank Electric Letter Opener (White) The SharpTank Letter Opener safely slices standard-sized envelopes. Our compact opener allows you to open letter quickly and neatly without taking up valuable desk space. Simply insert your letter into the slit and watch the magic happen. 2 mm cutting width designed for use with standard envelopes (note: this is not designed for use on cardboard). Requires 4 AA batteries (not included)