Natural stone knobs made from semi-precious stones, polished river stones and natural river stones are available mounted on your choice of stem. Included in the price are stems of black, brass, chrome and shiny nickel. For an additional $1.50 per knob you may have your stones mounted on heavier oil rubbed bronze or satin nickel stems. The knobs in the photos are not actually mounted, simply resting on a stem for your viewing pleasure.