I purchased this for my son to take on a high adventure scout trip this coming June. I looked it over when it arrived It seems to be of very good quailty. it is very large so fitting over a full pack should not be any hassle. I would give it a thumbs up. I can't give an item 5 stars without testing it first in the field.
I purchased this cover to be in compliance with Colorado blaze orange requirements. Colorado has already started ticketing hunters that wear a pack on their back and cover up their required 500 sq. in. of non-camo blaze orange. This cover "restores" blaze orange to the hunter as well as keeps a large pack/frame dry. The Colorado blaze orange req. for backpacks was also confirmed to me by email from Colorado Dept. of Wildlife, but it's not shown in their hunting publications. If you're planning to hunt Co. then get one of these.
With the lack of product information, I had no idea what I was getting into. I needed to cover a day-pack. I could cover myself and take a nap in this thing! While I'm sure that is great for someone with a large pack (50-70L) this just isn't appropriate for a day-pack.
I have no tangible means to rate this, and my rating is largely based on poor product information.