ID Help requested

[HKGuns]

Got this in the box with my Wilson Combat stripped lower.

Never seen anything like it before.

Does anyone know what this is? It was in a tiny ziplock bag.
https://uploads.tapatalk-cdn.com/20210520/b3896bfc488cf41f45a82fc6339ed42c.jpg

https://uploads.tapatalk-cdn.com/20210520/26b4ff8da5b24d3ce5239e9cb1784016.jpg
https://uploads.tapatalk-cdn.com/20210520/9de7c4feacc64d0c7a98c695b3855740.jpg

[ksubuck]

If your upper and lower have some play between them, you can slide that in the hole at the back of the fire control pocket under the takedown pin. It will tighten the fit up.

Sent from my SM-G975U using Tapatalk

[HKGuns]

So it’s a Wilson wedge!

Thanks I don’t use wedges.

[bamashooter]

https://www.ar15.com/forums/ar-15/What-is-this-cutout-in-my-lower-/118-721152/