Grease fitting thread tester gauge, thread size NPT ( 1/8 In,. 1/4 In., 3/8 In.), metric (M6 x 1, M6 x 0.75), metric (M8 x 1, M8 x 1.25), metric (M10 x 1, M10 x 1.5), BSPT ( 1/8 In. & 1/4 In.), UNF ( 1/4 In., 5/16 In., 3/8 In.), BSW ( 1/4 In., 5/16