I keep my CR-5 in my flight bag. The CR-5 is the smallest of the CR types at ~3 1/2". Pretty much haven't used any other type since the late '80s. Can't beat the convenience & accuracy of CRs compared to slide types. Still have my Kane slide type though for a memento & due to them becoming a rarity. Rather heavy due to the thick aluminium construction and lacks Mach No. scales.
Mind you, the whiz wheel I use the most is the slide rule on my watch. It's just so bloody handy as a calculator.