degree bend near one end, used in vertical navel piercings to position the decorative end of the jewelry more appropriately. They can be either internally threaded or externally threaded. Circular barbells Also known as horseshoe barbells due to their shape, they are used in any number of piercings, including earlobes, tragus piercings, nasal septum piercings, or even horizontal clitoral hood piercings, although the latter is less common, as the clitoris is deprived of the stimulation gained from a properly positioned captive bead ring. Surface bars Used in surface piercings. A surface bar is a barbell where the bar has a pair of 90 degree bends, in the same direction (similar to a staple), to allow the jewelry to be used for surface piercings. This design minimizes the pressure that would be caused by other jewelry designs that contribute to rejection in healing surface piercings. Surface bars are produced with many different lengths between the two points. Types of beads Beads for barbells can vary widely in design and appearance, although the vast majority of beads are simply spherical in design. That being said, any shape that threads can be tapped into can be used as a bead. Cubes, triangles, cylinders, cones, disks, and other basic shapes are common alternative bead designs. Some large gauge barbells, especially those used in tongue piercings, use "smartie beads", flattened circular beads, to prevent the jewelry from damaging the gums and teeth and allowing free movement of the tongue. There also exist "bondage" beads, which are dimpled to accept a captive bead ring, or the "koosh" bead which is a bead made of a rubbery material textured like a French tickler condom threaded to fit the tip of a barbell. Miniature vibrators also exist, in a variety of hard or soft materials on the exterior of the bead. Materials Barbell style jewelry can and is made from any metal appropriate for making body jewellery. Flexible barbells made from Teflon or tygon tubing are often used in experimental surface or deep tissue piercings. Beads do not penetrate the body, so often materials not usually considered safe for piercing can be used in a decorative manner such as acrylic, glass, or organic materials. History and culture Although at first glance the manufacture of threaded jewelry might appear to be of contemporary origin, there are examples of externally threaded, straight barbells being used by tribal people, most notably