If flexibility is what you need, the Classic99 6 Inch Retractable Utility Knife delivers. It has a three-position retractable blade made of carbon alloy steel that can handle all types of professional and home improvement jobs.
 
Includes handle and 3 heavy-duty metal utility blades
Handle crafted with steel for lasting durability
Easily cuts a variety of materials including cardboard boxes and foam
Interlocking nose holds blades securely for safe operation
Retractable blade design ensures safety when not in use
3 replacement blades can be stored in handle
Classic utility knife design