The SSA and SSF are the only on3s to be submitted to get approval from my knowledge, they haven’t tested any of the others but that doesn’t mean they wouldn’t pass. The only difference between the SSA and SD-C is curved trigger vs flat face. Same with SSA-E and SD-E, I like flat face triggers and prefer the E but would be happy with a C if limited to it. If I couldn’t run Geissele’s I’d run a an ALG , if not that a stock GI trigger as I’ve seen other brands fail.