Hey guys,
here is a stupid question

I dissasembled my impulse yesterday to change circuit-board. And when I had assembled everything back again, a plastic bumper remained

I can't figure out where it belongs haha.
To get to the circuit board I had to dissasemble the regulator from the rest of the marker. So maybe it came from there?
The plastic bumper is white, 0,05 inch thick, and the diameter 0,63 inch and has a hole in it which is 0,2 inch.
Anyone that recognize this?

Regards Robin