if you wear nikes i don't really think spk's are the boot for you, i can't wear nikes cuz they're to narrow since i have a wide forefoot - which is why i rock spks. I have a 9.5 almost 10 foot, my foot measure between 27.5 and 28 and I use 27 spk's. The liner packs out soooo much its ridiculous - like posted above. (i have the kaos so can't vouch for the pro liner) I ended up putiting a dr scholls insert underneath the liner just to fill some vertical space. The two buckle design is shit. yeah sure it cuts down weight, but how much? like 2-3 oz on each boot, not a big deal. plus the boot has the worst heel hold you can imagine, which is a result from the two buckle design, the front buckle is like half way down your foot so its just not in the right spot to hold the back of your foot and heel down. and the top buckle is too high to hold your heel back. with this said its obvious the boot has some big down falls mainly just the two buckle design and a liner that packs out way too much, but it does have its attributes, it is super super light, the shell is hollow in some places and its not very thick (could have some bad side effects, but whatever) the power strap is huge, and its easy put on if they're room temp. If they made a four buckle spk with a better liner i guess i might try it.