I have several ... different sizes, different brands. The last one I bought is the winner, hands down. It is Olfa ergonomic rotary cutter (45mm). I have other Olfa cutters, but none like this where the blade pops back into the safety zone when I let go of the handle (it also has a blade lock, but I never use it). It's for left- or right-handers. This one is plastic, but when I bought it, I saw a metal one with the exact same ergonomic design for over $60.00 ... waaaay out of my budget.