Stupid Question - What's This Part?

[Nothingtoxic]

May seem like a stupid question but I’m wondering if anyone can tell me what this part is and what it does. ICS gun. Thanks 

[alxndrhll]

I believe that's the hop adjustment lever (or 'trajectory adjustor' as ICS call it in the manual).

 

Source: ICS MP5 Manual

[Nothingtoxic]

9 minutes ago, alxndrhll said:

I believe that's the hop adjustment lever (or 'trajectory adjustor' as ICS call it in the manual).

 

Source: ICS MP5 Manual

Thanks for letting me know 👍

[Samwise]

Yup, I can conform that is the hop adjustment lever

They do tend to vibrate loose during use so it's often a good idea to put a wide shim and even a small o-ring under the screw that holds the primary hop arm in place on the chamber. 
The one that the lever you've pictured goes in to at the bottom.