Yellow canisters are commonly made of glass, earthenware (ceramic), or polypropylene. Lids are typically plastic, earthenware, or polypropylene.
Many yellow canisters use tight-fitting or press-fit lids and advertise leak-resistant seals. These features are commonly promoted to help keep food fresh and make containers more portable.
Yes—stackable and nesting designs are common. Many sets are described as stackable or able to nest inside one another for efficient cabinet and refrigerator storage.
Set sizes vary widely. Examples include 14-piece, 8-piece, 7-piece, 6-piece, 4-piece, and 3-piece sets, so you can find both large collections and small starter sets.