AR Upper Cover

Not sure who's upper I modeled this off.. so thanks to everyone who has ever put out a file! I know there's a few versions out there but I don't like supports and I like short print times so here we are….The holes for the string is 4mm use what ever, I put the pin in prior to tying the knot so I know it is not to short.the pins are different sizes, if you have any issues, questions, comments, or ideas please let me know! Please Note:this is designed for Replicas, displays and airsoft and is not for use on an actual weapons.