These sets are  actually two different sized bags. and they are quite a bit bigger than I would have thought. They are simple to use and save tons of space! You can roll them but what works for me is to flat-pack my items in the compressions bags, seal the end, and then kind of lay on the bag to force the air out. The resulting flattened pack fits my carry-on perfectly and the space-saving is remarkable!

Used on only one trip so far, but we are frequent travelers and these seem to be pretty durable, so I expect them to last a while.

Excellent product!

Update, June 2014: We have used them on at least five trips now, and they are still going strong.