Works like a charm. I strapped it in the back of my truck, took it 400 miles though rain, fog, and mist (the whole trip.....). Then it sat empty in the bed of the truck for almost a week, in rain, fog, and mist off and on. Then we reloaded with luggage for four, Christmas gifts, etc and made the 400 mile trip back. Hit more rain and fog during the last 100 miles or so. Everything stayed dry and never saw a drop of water in the bag.The size could be bigger. I have a full size truck and with a family of four and additional cargo such as gifts for xmas, the bag was FULL on our way back. Could have used a few more cubic feet for that trip. I'd like to see it sized to fill more of my bed, but I get the dimension choice they made to fit most trucks.The zipper worked fine. Be sure to get the inner "flap" pointed up and the outer "flap" of vinyl pointed down, and I don't see any way this thing could leak. I put a pretty good strain on it for the return leg of the trip mentioned above (read zipper was tight and had some tension on the teeth) and it did fine.If you've ever used those inflatable pools from the big box stores, its the same stuff, only thicker. Its pretty stout.I let it dry out and rolled it up today. The storage bag is a tad over sized, so if you don't get it rolled up just like they did at the factory, it will still fit. Material of the bag seems a bit flimsy compared to the truck bag itself. It sees like it will wear out pretty quick.But all in all, great bag, worked as advertised. Can't beat that!