This is a hook eye made to insert into an empty socket.

The inner diameter is 10mm from hex face to face.

I personally made it so I could hang a carabiner from my HSW. Specifically the one shown in the image: [https://www.printables.com/model/207725-carabiner](https://www.printables.com/model/207725-carabiner) It could be used for any number of hook style attachments as well though.

Prints with a little bit of support material on the bottom in the orientation shown. I think you could stand it up on the back of the peg and have it bridge the far end of the ring as well, but have not experimented with that.