The ball is typically under a millimeter in diameter and made of brass, steel, or tungsten carbide.[3] The ink, due to its high viscosity, does not permeate through paper and does not leave the tip of the pen by capillary action. As such, a bare minimum amount of ink is dispensed, with the result that the writing dries almost instantly and ink lasts longer than it does in other types of pen. Ballpoint pens are reliable, versatile and robust, and are available for a very wide range of prices.