The metal spring or spring element with OEM no. 4931506540 is a genuine Milwaukee part for Milwaukee Tool, including :
M12FCIWP12G3-0 1/2in IMPACT WRENCH
M12FROS2.5-502X M12 FUEL Random Orbital Sander
M12FCIWF38G3-502X 3/8in IMPACT WRENCH
M12FDGS-0 F. STRAIGHT DIE GRINDER
Milwaukee M12FROS5-5252X
M12FROS5-0 150MM R.O.S. 5MM Orbital Sander