I used to think these packing cubes were silly but I don't think I can travel without them now.  Like other reviewers have said, they make packing a lot faster especially when you're moving to a different hotel every night, and going through stuff in your luggage a lot easier since things are more compartmentalized.  They also keep clothes neater since they they're packed tightly and don't shuffle around.  I could fit all of my summer clothes for a 2-week trip in three of these small cubes.  The zippers are smooth and sturdy, and the handles on the sides are great for carrying.  Works well in a wheeled carry-on or regular backpack.