Annoyed by gas spilling everywhere when filling your GBB mags? Then Hush is your answer!
Once these O-Rings are placed over your fill valve you will be able to silently fill your magazine without causing any gas spills. This is a renown inconvenience for some brands of GBBs, more specifically TM (but will work in competing brands).
And of course, they come in a charming yellow.
5x Hush Fill Valve O-Rings