This is the wing that clamps down and holds your glass plates in place when casting your own acrylamide mini gel. The nubs do not seem to be standardized on all commercial clamps, but I made this one for my large one, and it fits my small one with a bit of filing (I didn’t realize the size was even different until I broke the second one lol). Compatible with the Bio-Rad mini protean 3 system, hope it saves someone a few bucks.