You get a lot for your money when you buy this luggage set: for only around $50, you have three larger rolling bags and two smaller ones. The large bags have retractable handles as well as regular suitcase-like handles on the side, so you can both pull and carry them. Each bag has lots of additional zipped compartments / pockets.
The set is made of polyester. It works best for flying: the larger ones hold as much as medium-sized suitcases, they can be checked in as regular luggage, and two small bags are perfect as carry-ons. Retractable handles and wheels are priceless in airports when you have to walk with your luggage - pulling it is much easier than carrying as the large ones can get pretty heavy.
Our bags have been through several domestic and a couple of international flights. The international ones turned out to be rough on them, I have noticed some visible wear. I guess I expected more durability, but I'm not worried about that: for a price like this, I'll just go and get another set when this one starts falling apart.