With each use of the air tool, a fine mist of precisely metered oil enters the air stream. Technician always sees oil supply and oiling action. Holds three to four days supply of oil. High quality aircraft aluminum stem. Oil reservoir is made of high impact plastic. All internal moving parts are coated and lubricated. Use on all 3/8" and 1/2' air impact guns, air wrenches, body shop air tools and pneumatic hammers. 1/4" NPT Female inlet and 1/4" NPT Male outlet.