Heat tunnels in this category have openings ranging in size from six inches to 10 inches. Heat tunnels or shrink tunnels heat air around a package that is wrapped in shrink film. The heat causes the shrink film to form a tight seal around the product. Heat tunnels are usually designed with a conveyor belt to carry the product through the tunnel. Each tunnel has adjustable temperature controls. Shrink tunnels are useful for making multi-packs, as well as heat shrinking tamper evident bands on products.