UL has Classified certain breakers to be used in competitive panels, which makes them legal to use, the UBI breakers are for Zinsco, FPE, and Pushmatic panels, also Eaton has Classified breakers also, and Siemens, & Eaton, have UL Classified breakers for SQ D QO although I would not use those since QO is available from SQ D, the UBI breakers are the the only legal option, besides replacement. What do you do with panels that the brand name has changed but in reality still exists, like ITE, Cutler-Hammer, etc. ?