GHK AK Hop unit

[Trenchrunner]

Opened up the hop unit and this part popped out couldn't for the life of me figure out where it went and then I miraculously lost the part when trying to place it in the barrel housing. Now it's gone I'm wondering if it's worth buying another hop unit seen as theyre only £6 although even then I'd still be non the wiser on how these go together. Is the part nessisary? And where about's does it fit?

Thanks,
Bill

[Gunslinger]

Its basically the c clip that's on an AEG hop, it stops the inner barrel from twisting in the hop unit

[Trenchrunner]

Right yeah that's what I thought, might be a good idea replace it then don't want hop issues