I've got an Bakflip G2 on my 08' Silveardo. It is a folding cover (folds in four sections all the way up against the rear window for full bed access). I like it a lot. I ordered the regular which is made out of abs plastic. It weighs around 90 lbs.
They also make an all metal one, it is a couple hundred dollars more expensive.
I ordered from
realtruck.com. They had a special several months ago for like 20% off and free shipping, so it came out to be a great deal.
Bakflip G2
Bakflip G2 All Metal
I have had no leakage issues at all, when going through the touch-less car washes.
The cover can only be opened once the tailgate is opened. If your truck does not have the tail gate lock kit you can buy it from GM for like $40 or so.
Close the cover, lock the tailgate, and it is secure. Of course if somebody comes along with a crowbar they are going to get in, no matter what covering you have.
I can snap some pictures of it on my truck if you want.