Bulky but well protected, the Mk.35 is a single element suit which requires no additional protective or thermal regulation garments. Constant-volume hard joints combined with flexible limb and torso elements allow for full mobility, even in a vacuum, and the suit includes the option of a 100% oxygen supply for use at low pressures, air for normal pressures, or a 2% oxygen supply with nitrogen and helium for operations in high pressure environments. Though comfortable and easy to use, the Mk.35 is rarely used at low pressure and in hard vacuum, partly because of the need to decompress the wearer to prevent the suit 'ballooning', and also because of the bulky life-support system needed to maintain suit pressure.