Instrument for smoking weed. Different from tobacco pipes, pipes for smoking weed usually have a very small “bowl” that holds a small amount of ground plant material. They can be made of wood, metal, plastic, or, most commonly, glass. Glass pipes for smoking weed are usually small, brightly colored, and hollow on the inside. They are often quite cheap since they break easily and need to be replaced often. They are typically small and discreet as well.