Sea to Summit Travelling Light Compression Cells are sealed with a heavyduty zip-lock closure, and evacuated through a discrete, welded one-way valve in the base of the cell. They are completely hand operated, requiring no pump or vacuum cleaner to reduce your clothing volume by up to 80%. Compression Cells can be reused time and time again. As well as saving space, careful use of Travelling Light Compression Cells will help protect your clothes from wrinkles through whatever arduous journey you put them through. Travelling Light Compression Cells are available in packs of two: small and medium cells or medium and large cells.