Bob, the CX is one of OL's latest tweeks on his ACS limb. The CX limbs are carbon lams over an actionboo core, with no glass. As far as I'm concerned the increase in efficiency & energy storage aren't the main benefits of the CX limb. The shooting characteristics that ppl love about the ACS are enhanced by this new advancement & I consider that the biggest plus. I've never shot any other bow like it.