Response to Spike
Paul Parker here. I'm the Garmont ski boot Product Manager. Of course I give the Radium 5 Stars! More seriously, I wanted to reply to Spike's review and fit concerns.
Spike--Sorry that you aren't happy with your Radiums. I'd like to suggest a couple of things that might help out.The foam used in the liners of the Radium is the same foam composition as used in your Endorphin liners, just an improved design with a separate Strobel-stitched sole, new inner and outer skin, plastic-reinforced tongue for shin protection, and more cuff reinforcement, to name a few details. The fact that you find them uncomfortable and "hard" makes me wonder if there is an issue with the thermforming or fit, as feedback on fit has been consistently positive. You might get a shell fit from a boot fitter to be sure that you are in the right size. And, another thermoforming could be in order as well. Regarding walkability, these boots have more cuff travel in walk mode than any boot we've ever built. Be sure that you loosen the power strap, flip the walk mechanism's lever up to open it, open the cuff buckles completely, and use the Easy-Lock cuff catches in the biggest notch to give you the best range of motion. Following this routine, I think that you'll find that they walk very well. Spike, I hope that these suggestions are of some help and that you have better luck iwth your new boots--
Regarding flex index--Flag nailed it that flex index is random. There is no science in it. That said, Radiums are comparable to a 120-130 flex index, depending on the brand. We call it a 120 AT since it's not fair to compare alpine and AT boots. Radiums are quite stiff and handle big skis with ease. The High Overlap makes them especially quick and supportive in forward flex.
I hope these details are of some help--