Ortlieb Dry Bags are the lighest and best waterproof pack sacks - Available in 3, 7, 12, 22, 42 and 75 litres.
Price: £11.95 inc vat
Ortlieb's super light weight dry bag family in seven sizes allows both a clear and variable distinction of storage space; each dry bag is marked with its volume in litres.
Ortlieb Ultralight waterproof bags made of ultra light weight nylon fabric PS10 will keep kit dry even if your main pack won't. The reinforced round bottom is made of folding and tear resistant PS17 fabric and features a base loop for easier unpacking.