They must have made a typo in their instructions. Im a metric guy, and yes 3/16 makes sense, there are two 3/16 allens for up down/ left right adjustment of the entire sight, however the micro tiny allens must be 5/32" not 6/32. To move the pins slightly up and down. (there are two allens on each pin). Im guessing they meant 5/32 as it fits in there pretty good I guess, but I thought maybe it should be a little tighter. I just dont wanna round anything out.