They are drill guides, used with a jig, when drilling holes in firearm receivers. If you scroll way down in the first link, you will see a picture of the guides. I emailed the company that made the guide(80percentarms) and this was their reply. "Hello , Thank you for reaching out to us and for your patience! I sincerely apologize for any delays this may have caused you. We are trying our best to respond to all of our customers in a timely manner but we get hundreds of emails per week. I'm glad we were able to get to yours today! That is a drill guide that is used for our older jigs. Unfortunately, we have since moved onto producing our newer Easy Jig gen 3 jig seen here which eliminates the need for those drill guides: https://bit.ly/3yCCqOO Please do not hesitate to reach back out to us should you have any further questions or concerns! We are always here to help!" Hello , Thank you for reaching out to us and for your patience! I sincerely apologize for any delays this may have caused you. We are trying our best to respond to all of our customers in a timely manner but we get hundreds of emails per week. I'm glad we were able to get to yours today! That is a drill guide that is used for our older jigs. Unfortunately, we have since moved onto producing our newer Easy Jig gen 3 jig seen here which eliminates the need for those drill guides: https://bit.ly/3yCCqOO Please do not hesitate to reach back out to us should you have any further questions or concerns! We are always here to help!

They are drill guides, used with a jig, when drilling holes in firearm receivers. If you scroll way down in the first link, you will see a picture of the guides. I emailed the company that made the guide(80percentarms) and this was their reply. "Hello , Thank you for reaching out to us and for your patience! I sincerely apologize for any delays this may have caused you. We are trying our best to respond to all of our customers in a timely manner but we get hundreds of emails per week. I'm glad we were able to get to yours today! That is a drill guide that is used for our older jigs. Unfortunately, we have since moved onto producing our newer Easy Jig gen 3 jig seen here which eliminates the need for those drill guides: https://bit.ly/3yCCqOO Please do not hesitate to reach back out to us should you have any further questions or concerns! We are always here to help!" Hello , Thank you for reaching out to us and for your patience! I sincerely apologize for any delays this may have caused you. We are trying our best to respond to all of our customers in a timely manner but we get hundreds of emails per week. I'm glad we were able to get to yours today! That is a drill guide that is used for our older jigs. Unfortunately, we have since moved onto producing our newer Easy Jig gen 3 jig seen here which eliminates the need for those drill guides: https://bit.ly/3yCCqOO Please do not hesitate to reach back out to us should you have any further questions or concerns! We are always here to help!

References:

https://mobile.twitter.com/80percentarms

https://www.80percentarms.com/