These instruments can come in a variety of sizes and shapes. The most common are tubular or egg shaped and can be made of metal or plastic. Some creative percussionists have made them out of cans, film canisters, milk bottles, etc. There are even square shaped tube shakers that allow for greater rhythmic definition. They can be filled with all types of beads, pellets, sand, rocks, rice, seeds, etc. creating different sounds and volume capabilities.