StealthFormula

I just picked up a used set of 30lb. SVO's for a good price but I am confused by a couple things. The top four have letters A, B, C and D on them. The bottom four have A, A, C, D. Does that sound right? Both D's have a mesh thing at the bottom where the others have a needle type thing. My buddies got them on his Stang but all of his are one letter and the bottoms are all like the mesh and installed in no particular order.