Primary Arms GLX Anti-reflection device.

This little aluminum device screws into the GLX 1X and provides anti-refelction properties aswell as shade from the sun to reduce glare on the optic.  New in package.

Fits some other optics also but you'd need to verify yourself. 

https://rdsc.ca/primary-arms-glx-1x-microprism-anti-reflection-device.html

Prefer local sale. Shipping is on buyer.