definitely rainproof
We traveled from Alabama to New York - DC - NC. it rain for most of the trip and items were dry. But you MUST follow instuctions. On the second lag of our trip the bag was put on the roof upside downour bags got soaked along with most of our clothing inside the luggage. VERY large and we were able to put a 29 inch, two 25 inch bags a duffle bag and childs carry-on (19 inch) with a little room to spare for a blanket or two.

Good Product for the Price
Plenty of room and easy to use. Kept everything dry on a four day road trip. Worked as advertised.

it did the job
We packed it full and drove over 1000 miles while on vacation without a hitch. It didn't leak while driving through the rain and the review I read about costing fuel mileage proved false. The zipper only opens 2 sides so it was a little bit of a challenge to pack, but it was worth the money. The tie down straps that came with it are really cheap, so I just tossed them out and used a couple of good quality ratchet straps. After 1000 miles of travel and packing and unpacking at our destinations, it is still like new. Its well constructed and well worth the money.

Quiet and Roomy
We've had a rain-x top carrier before but this was much better. It seems roomier and is much more quiet as the straps don't blow around and hit the car. The price was also almost half as cheap. As far, as all the reviews go about poor gas mileage....of course you're going to get a little less miles to the gallon as you have all this extra baggage and weight on top of your vehicle but you have that with all the top carriers. Very pleased!

Didn't hold up.
We have taken this bag on two large trips. Both trips were in excess of 4 hours each way and it rained at least one way on each trip. In both cases, the bag held a significant amount of cargo and kept it dry. The problem is that on the second trip, 2 of the 4 straps tore off the bag. We are lucky that the bag stayed on top of the car, because it could have caused significant damage if it flew off. The other problem is that we cannot use the bag for the return trip, yet we still need a roof-top carrier, so we are going to have to get a different bag quickly.