Seems there's 2 types of center fin set screws... ones with a metal "nut" (square bit that locks fin to fin box) and the "breakaway" type that is a brass fitting set into plastic. The plastic type is designed to let the fin break the screw instead of damaging your board if you catch a fin in the sand or on a rock.
I just bought a new center fin (FCS Soul Flex) from a shop who's owner is argueably the the top surf guru in my area. He insisted on giving me a "breakaway" type of set screw (for the reasons above).
I HAD a breakaway type on my board this summer and almost lost my fin when it broke ( don't think I hit anyting or caught a fin...). When I walked across the street (yes... the break I frequent I'm lucky enough to have a REALLY good surf shop across the street!) to get a replacement screw to reset the fin, the guys at that shop insist that metal ones are better because they won't break.
What's your take? Do you use the breakaway type or all metal?? I'm sticking with metal...I feel like if I catch a fin hard enough to break a "breakaway" I'll still damage my board and possibly lose the fin, but the metal ones won't break.