Space Bags

You get the air out by rolling up tightly and squeezing. I have used the medium size ones for traveling. For bulky things like fleece or sweater it really saves room. For other things like t-shirts and knit pants, etc it doesn't save much room but does reduce wrinkles if done right.

Or use the biggest zip-loc bags -- zip almost closed, sit on the bag to get air out and zip all the way shut. Worked to pack a down jacket in a much smaller space.

The same. Zipper lock bags come as large as 2.5 gallons which is more than enough for even the most bulky items. Space bags are another item (IMO) that is over priced for the benefit received.

Like others have said, if you have some bulky items to pack it might be worth it to use a Ziplock space saver bag. It wouldn't make much difference for packing a typical summer type wardrobe though. On our most recent trip we took some medium sized bags with us laid out flat in the bottom of our suitcases. This was because we were planning to buy some more 80"x80" (cm!) down pillows in Germany. It worked really well for this application!

Edit: Our son's family took 2 space bags also because they were traveling from Istanbul to Paris to London to the Isle of Skye where they needed some fleece and down jackets for the week they were there.

It was really easy to roll/squeeze the air out of them and they actually didn't try to reinflate. We use some larger space bags with our ski clothing in the U.S. and there was always a problem with the seal over time. With the new Ziplock brands I bought for this trip, they kept a tight seal.

I put my heavy jacket in a regular SpaceBag GOING to Germany, then brought back two down pillows coming home. I just called the desk of our hotel to borrow a vacuum with a hose attachment. Not a problem.