Conservation. Glass gauges replacing steel. Checking the outside diameter of a gear with one of the glass ring gauges, that are replacing steel gauges at the Frankford Arsenal. 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