DynaFlo® 3/8″- Straight Steel Yellow Zinc Drive Grease Fitting Without Ball Check. Type Grease Fitting without Ball Check. Finish Zinc – Yellow. Grease fittings are heat treated to SAE J534 specification with hardness on greasing end to a minimum of 83 on Rockwell 15N scale with a case depth of 0.005″ (0.13 mm) to 0.009″ (0.23 mm).