From the manufacturer:
X-ACTO is excited to announce its first fully retractable, safe #1 Knife. Easily change the blade as you would with any X-ACTO #1 Knife. The soft, triangle shape comfort grip provides extra control. The knife is perfect for delicate, precision cutting and trimming of paper, plastic, balsa, thin metal, cloth, and film. The anti-roll handle keeps the knife from rolling off your work surface.