Stack up to 10 high integral support columns allow the crates to be stacked when full without damaging the contents nests when empty thus saving valuable storage space solid or vented choose solid sides and base, solid sides with vented base, or a totally vented crate; whichever suits your application manufactured from UV stabilised polypropylene they are strong, durable and relatively lightweight standard colours include white, red, green and blue.Solid crate pictured with optional 2 piece lid system.