NPT Thread Sizing Info 1/8 NPT: 0.405 Roughly 3/8". 1/4 NPT: 0.540 Roughly 1/2. 3/8 NPT: 0.675 Roughly 5/8". 1/2 NPT: 0.840 Roughly 7/8". Type: Push To Connect Straight Fitting. Vacuum: 0-29.5 in Hg, 750 mm Hg.
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