Never got the "burp" of expelled air I expected. Discovered the best way to push air out is to squeeze or roll it out like with a normal dry bag except the air comes out the port instead of the top.I picked this up to replace my my surplus sealine bag with the manually operated valve.I stuck everything in a surplus ILBE ruck sack and through it in the back of a pickup truck. It kept everything dry in the rain at 60+mph for about 300 miles.The air valve did stick open when I was purging it once. I found you have to get the air to move a little faster to prevent that.Great dry sacks for just about any adventureI own several "normal" dry bags from multiple manufacturers and all work as expected. I was intrigued by the one way valve on this one since I was looking for a way to tightly pack down a jacket to keep in my trail running pack. Quality seems good but the valve doesn't perform as expected. I inserted the jacket, squeezed out the air and was pleasantly surprised by the vacuum seal look of the bag. Unfortunately, this only lasted a few minutes. The bag slowly filled up with air again and it looked like any other dry bag I have. I'll keep this one but will continue to look for a better option.Great bag to keep everything dry and not take up wasted space like a balloon.This is one of the lightest vented dry sacks I have found. I am using it to compress my Down sleeping bag and it does a great job. The mouth is a bit narrow though, so if you are getting it for a sleeping bag sack, be sure you check the rolled or stuffed diameter of your bag before purchasing.I have 5 other SealLine Blocker dry bags, and they are all great. The reason for three stars on this one is that the PurgeAir Valve does not work very well. It takes massive pressure and time to get the air out. Like literally I have to sit on it to get air out, and it comes out so slowly that I finally lose patience and deal with it the same way I use other dry bags without the valve. This is a great idea poorly executed. I am returning itAfter squeezing air out through the the valve, I expected it to stay, but it just let air back in.Strongly made and ingenious this is a top of the range dry sack. Having used it while cycle camping the birght orange colour if very noticeable whilst on the bike which is a real boon for safety. The material is also very strong having got it jammed on arear cog I was worried it would rip but aside from a dab of oil which came off it is good as newSeal Line has solved the problem of getting most of the air out of your dry back with the air purge valve. I can seal the bag and put light pressure on the bag to squeeze the remaining air out of the bag and it does not leak back in and expand over time. Impressed.The bag is made of verry thin material compared to PVC bags. The valve worked well. But, the main problem is that at my verry fist bath test, water made its way in from the opening even if I carfully rolled 3 time the bag top. It is not the way I rolled it but the material that doesn't tie together well. Also, description says made in U.S.A. but the package and tag says made in china..Awesome bag. Kept my stuff dry and it was able to be moulded to the space I had (was packing in a kayak). I have other deadline bags and this is just as good!aucun souci ,l'article correspond a ma commande.