I work for a major automotive OEM with about 1500 employees in my building alone. I set a limit to 3" (7.62cm) for my main EDC which is a Spyderco Sage 3 CF. I also carry a Vic Cadet for the "sheeple moments". Working in IS I use my Sage often though the day opening packages, cutting up server boxes, plastic strapping, Cat6 cabling, etc. But it is usually back in the secluded data center. I also see a lot of people thoughout the day in a support role so I have many opportunities to offend just the right sheeple. Which explains my choice for the Sage 3 CF and the Vic Cadet. The Sage carries very low and the superb deep-carry wire clip makes it practically invisible. And when I do need to cut something in the general public, out comes my Cadet. I've carried other folders that were a bit bigger and up to an Endura G10 which is a hair shy of 4". But carrying something larger than 3" worries me so I don't do it.