I don't know if anybody's interested in this but it is P2 information. I ordered a set of 9450 blades from MakoMoto thru Amazon for my P2. The ad clearly stated 9450. I received them today. The number stamped on them is 9443 (CCW)R and 9443 (CW). I already contacted Amazon and they will refund my money 3 days after they get them back. I understand accidents happen but it really shouldn't have. I don't know the difference other than what I've read about the 43 series letting the quad descend too fast and causing crashes. I have flexed both of them and the 50's are considerably stiffer which I would think may offer more lift and stability. But I'm new and I'm just guessing. I think it will fly with both models but I don't know what would happen if you accidentally mixed them up and had some combination of both model blades on your quad at the same time. What if a newbie got these in the mail and didn't know to check them and only put one or two or three on. Once again I don't know but I don't think it would fly as solidly as if all four blades were the same. To be fair I should mention that Amazon made the return process quite painless. They sent me a label with the shipping prepaid which I printed and put on an empty box with the blades inside. I am instructed to put it in my mailbox and the mailman will pick it up tomorrow. That really makes it easy, but it's still a hassle and I think it's MakoMoto's fault.