My Utility Knife - now with optional keyring hole

I work retail and open boxes and packages all day. I need a utility knife I can carry in my pocket, open with one hand, and change the blade when dull. 

• This little guy is 6mm thick and rounded all around for easy carry. 
• The textured thumb pad gives grip for sliding the blade forward and back. 
• Locks in position forward and back.
• Dimensions are ~72mm long, 28mm wide, 6mm thick
• Using .2mm resolution and PETG, it takes about 45 minutes to print and consumes about 3m or filament. 

Caution: It is a small, thin, knife that uses a razor for the blade. Be careful. It's not for carving or prying. Use your head.

EDIT: Someone asked for a hole so it can be hung from a keyring. Why people want stuff hanging off their keyring, I'll never know, but who am I to argue? Files identified with “Keyhole . . . ” have a 5mm hole so the knife can be attached to a keyring.