Air Hose for Pneumatic Tools 1/4 in. Male x 3/8 in. Female Brass Pipe Reducer Coupler Connector Fitting 150 PSI Maximum 1/4 in 18 NPT Home Garage or Professional Shop: Amazon.com: Industrial & Scientific
Everbilt 3/8 in. Barb x 1/4 in. MIP Brass Adapter Fitting 800029 - The Home Depot
Dorman 3/8 X 1/4 Inch NPT Fuel Hose Fitting 785-416D | O'Reilly Auto P
LTWFITTING 3/8 in. ID Hose Barb x 1/4 in. FIP Lead Free Brass Adapter Fitting (5-Pack) HFLF39156405 - The Home Depot