Any cutting operation, including reaming, leaves microscopic projections or burrs on the processed surface. After reaming, an in-process barrel can be taken to the rifling stage and still produce a decent barrel. However, high-grade barrels or those destined to fire soft lead bullets may be polished (called lapping) prior to rifling. Typical bore lapping uses an abrasive paste on a soft lead cylinder. It is passed through the bore several times, reducing any burrs. The size of imperfections is minimized by applying a fine grinding paste. Finer grade grit paste produces smoother surfaces. If required, pastes (properly graded for grit size) can produce a mirror finish in metals.