Set of three washers for AEG M4/M16/AR15. They will allow you to adjust distance between pistol grip and gearbox shell in the way that pistol grip will not touch lower receiver.

This allows to precisely adjust AEG motor & make it sound nice and lower wear on the gears

  

They come in 3 thicknesses: 0,4; 0,6; 0,8mm and this will give you combinations: 0,4; 0,6; 0,8; 1; 1,2; 1,4; 1,8mm