Conservation. Glass gauges replacing steel. A steel plug gauge is compared with a glass plug gauge which replaces it at the Frankford Arsenal. A plain ring glass gauge shows in the foreground. Glass gauges are lighter and cheaper than steel, permit greatly 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