There is a large variety of jewelry available for stretched piercings. Many jewelry materials can be used in the manufacturing of jewelry for stretched piercings; materials that would ordinarily be too delicate or brittle to be inserted in smaller-gauge piercings are freely used. Stone, fossilized materials, wood, bone, horn, amber, bamboo, silicone, and glass are not uncommon in stretched piercings. Some of these materials "breathe" better than metals or plastics, preventing the buildup of sebum in the enlarged ear lobe. Jewelry, however, is still often made of acrylic or metal. There are dangers associated with wearing porous materials such as acrylic, stone, wood, bamboo, horn, bone, or other materials with small or microscopic holes, in a freshly stretched piercing. These materials not only have microscopic holes that will trap bacteria and can cause infection, but also cannot be autoclaved or properly sanitized, and are therefore unfit for a fresh stretch or piercing. The best materials for a fresh stretch that is not vulnerable to bacteria are implant grade steel, titanium, and glass. This is because these materials are non-porous and can withstand the heat and pressure of an autoclave, so that they can be properly sanitized before insertion.