Conservation. Glass gauges replacing steel. A steel plug gauge, since replaced by a glass gauge at the Frankford Arsenal, is shown checking an inside diameter of a cartridge case. Glass gauges are lighter and cheaper than steel, permit greater visibility in inspection, are not as much affected by room temperatures and heat of operators' hands, are not corroded by perspiration, need no protection against rusting, do not acquire burrs that would change the effective sizes. They can save the annual use of 250 tons of critical tool steel in government arsenals alone