Basically, a packing cube is a simple fabric-and-mesh bag that tidily zips away your things, which helps during travel. Different cubes for different things.
Good packing cubes are made from high-quality fabrics and help you with organizing and accessing your clothing and small items.
The best packing cube: Eagle Creek Pack-It Original Cube Set (solid build quality)
The second best packing cube: eBags Packing Cubes (larger cube size, in 12 colors)
The best packing cube upgrade: Eagle Creek Pack-It Specter Tech Cube Set (light, full-zip design for better access)
The best affordable paking cube: AmazonBasics Packing Cubes (eBag like shape and size, good pricing)