Cylinders are objects that have a circular cross-section and a straight length. They can be made of various materials, such as metal, plastic, or wood. Two crossword solutions for the term cylinders are 'TUBES' (5 letters) and 'SPOOLS' (6 letters). TUBES are hollow cylinders that are often used to transport liquids or gases, while SPOOLS are cylindrical objects with a hole in the center, which are typically used to store or transport thread, wire, or rope.