I'm purchasing parts for my SBR build and just noticed a choice in size when I was about to order a set of KNS pins. (Yes, I know some people think they are a waste of money, but alot of time and paperwork went into this receiver, so $30 is cheap if it works)
I have a choice of...
0.154
0.155
0.170
I imagine the last/largest is for COLT lowers, but what's the difference between the first two?