Some pipe makers and retailers readily admit that not all bent pipes pass pipe cleaners. A number of pipe smokers insist that by bending the end of the pipe cleaner a little, or some other adjustment, all their bent pipes will. I'm of the previous opinion. I'm always especially impressed when significantly bent pipes pass a pipe cleaner, like my elegant smooth bent Rhodesian by the Austrian pipe maker Kemberling, or my little econo-pipe from Nording, an Eriksen. But other good smokers don't pass a pipe cleaner. Usually with those, as long as the airway is open, I just pipe-cleaner the stem, and then I take off the stem and pipe clean each half as needed, which means not too often. All straight pipes or slightly bent pipes should pass a cleaner, unless their is a stinger or filter in there, which you should immediately ascertain when you buy a pipe. For the folks who can pipe cleaner any bent pipe they've ever handled, I commend them on their dexterity.