This is the site for Over Board:
http://www.over-board.co.uk/duffels/waterproof-duffel-bags.htmlI would have to look as to whether ours is the 90 or 130 litre, but there are two advantages to these bags.
The first is that the end straps secure the bag to the rack. No other fastener is needed, although I tend to use an elasticated spider as a belt & braces.
The second is that the bags have a handle on each end, which means that I and MrsW can handle it easily, although it does resemble a body bag.
