A fit system positionable adjacent interior portions of a helmet and cranial surfaces of a cranium of a wearer of the helmet proximate the interior portions of the helmet for improving the fit of the helmet to the cranium. The system includes an elongate fluid impervious bladder having a first end including an inlet port in fluid communication with the bladder and a second end remote from the first end. The bladder defines a single continuous fluid flowpath between the first end and the second end for receiving fluid introducible into the bladder through the inlet port for expanding the bladder so that substantially the entire length of the bladder may be expanded to engage mutually facing portions of the cranium of the user and interior portions of the helmet. The bladder is positionable within the helmet so as to substantially wrap around side portions of the cranium, temple areas of the cranium, a rear occipital protuberance portion of the cranium and an upper portion of the cranium without compromising the fluid flow path.