Could someone please let me know the difference between the M12's and M12's Series 2. It appears one difference might be that the series 2 are not fused. I have a pair of 10's, 7's and 5's, and am looking to pick up 12's. My 10's are fused. I seem to recall that 10's came as 10A and 10B. It would save me a lot of time if someone could help me out with this. Thanks a lot.