A joint connects two separate pieces of glass. Every joint has a male and a female component that fit together, one inside the other. Joints are measured by their diameter, and the standard for the pipe industry is 14mm. 10mm and 19mm joints are also common alternatives. Standardized joints allow accessories like bowls, nails, and ash catchers to be purchased, customized, replaced, and cleaned separately. Most joints are ground, giving them a texture that creates friction between the two joint components so that they can't pull apart accidentally. Because of this texture, most ground joints have a matte, almost opaque appearance. GRAV® has begun flame polishing our joints. After they're ground, our glass artists use a torch to polish down the rough edges, keeping the useful texture but eliminating the cloudy finish. Ground joints are usually secure enough to prevent components from slipping, but joint clamps (available from GRAV® in all three standard sizes in either plastic or stainless steel) can be used for additional stability and peace of mind. Joint clamps fit around the two sides of a joint like a belt, locking them in place.