UPDATE - Ok... it does leak. I certainly would never call it "Water Proof" it is more "Water Resistant" so you definitely want to pack things in garbage bags if you want to keep the contents completely dry.We have been considering a roof top cargo bag for several years. It seems like we are running out of room when we travel. Our solution had always been to just be more judicious in what we packed, but now that we have a baby we began to run out of options. Enter the Keeper Waterproof Roof Top Cargo Bag.Some General Notes+ This thing holds A LOT of stuff. In fact, it really is like a second trunk. We were able to fit two big duffle bags into the cargo bag and still have plenty of additional space.+ Now quite proof - more like "Water Resistant". The cargo bag only has one zipper which is hidden under a double-flap that velcros together. On our trip we only experienced a light snow, but everything remained dry.+ The Zipper works pretty well - I have noticed in many duffel bags (and backpacks) that the zipper is the thing that typically fails. So far we have not had a problem with this cargo bag (I will update my review if it does fail)Other things to considerIf you are purchasing the Keeper Roof Top Cargo Bag you may also want to considerSherpak SuperMat Roof Matfor the protection of your roof. The Supermat also provides an anti-slip surface and should also help with gas mileage since it works as an additional wind barrier (between the cargo bag and your vehicles roof).- This thing will wreck havoc on your gas mileage. For us we lost about 3-4MPGS and that is with the Supermat.- Not the easiest thing to tie-down. The fasteners and straps are mediocre at best so it was a bit of a challenge to get this thing tight to the roof.- Consider packing during the day - the bag and the fasteners are black, so without the use of a flashlight it is very difficult attaching this thing at nightOne more piece of advice, once the cargo bag is loaded make sure you do a test drive at the maximum speed you intend on driving. Once you return doube check all of the straps and do a little secondary tightening.Final Verdict - While it was a little difficult fastening to the roof the Keeper Cargo Bag met my expectations.4 Stars