Thank you sir. I knew you would know the answer.
I don’t know what the F mark means.
I’m still learnin as fast as I can.
‘F’ mark is for a flat top AR
Lewis Machine Tool makes a really good non-folding sight that will work with almost anything, since you can adjust the elevation as well.
http://www.lewismachine.net/product.php?p=65&cid=2