The air trapped in a tuilik makes rolling easier. If the paddler comes out of their kayak, a tuilik provides considerable initial buoyancy, and the legs may be drawn up into the air pocket. PFDs may be worn over or under a tuilik or tuiliusaq.
Many kayakers do not use a tuilik, but instead a separate spray skirt and kayaking top (often a drytop, something like a drysuit jacket), which usually seals around the waist, arms, and neck. A tuilik integrates the skirt and top into one piece of clothing, with a hood-edge seal rather than a neck seal. Tuiliks are generally less restrictive of motion, but the fit is finnickier.
The hood must fit snugly, but the arms and body fit loosely to allow free movement and clothing underneath. Rolling requires extra length in the torso. Quick-release suspenders were traditionally used to lift the front and prevent water from pooling in the excess length. The tuilik must seal at the face and kayak cockpit coaming, and usually at the wrists (unless there are integrated mittens, as in the tuilikusaq image above).
Traditional tuiliks are narrower, to fit narrow custom-fitted cockpits; mass-produced kayaks have larger cockpits (including long keyhole cockpits) and the tuilik must therefore be wider at the hem. Some tuiliks are made with double decks to fit a range of cockpits.
Commercial tuiliks may be custom-fitted or made in a broad range of off-the-peg shapes and sizes (one manufacturer stocks 15 sizes).
Traditionally, a tuilik can be made from specially-prepared seal-skin, sewn with sinew, with draw-string seals. A sealskin tuilik is soaked, stretched, rubbed, and greased to keep it soft and waterproof.