These professionally styled, lightweight, and compact trimmers are safe, accurate, and precise. Their patented self-sharpening blades cut in either direction and are enclosed in tough plastic housing, so the blade is exposed only to the cutting edge.Each trimmer also features an automatic paper clamp that holds work securely, a metal base with preprinted guides for precise cuts, and an imprinted protractor for angled cuts.Dahle Personal Rolling Trimmers are ideal for precision cutting of photocopies, photographs, films, computer paper, facsimile paper, tissue paper and other lightweight materials. They can cut up to seven sheets of paper at a time.Model 500 measures 14 1/8 in. x 8 1/4 in. and has a 9 in. cut length.Model 507 measures 17 in. x 8 1/4 in. and has a 12 1/2 in. cut length.Model 508 measures 22 1/2 in. x 8 1/4 in. and has an 18 in. cut length.Replacement rotary cutting head (sold separately) fits all three models.