You can check GT's website for any info you need. They are a 300 spine which is much stiffer than the 5575 (400). However, as Rick says they are pretty verstile. I am using them for hunting at 27" and 45# and they fly incredibly well. Of course they shot well at 58# last year as well.

Don't let the term ultralite anravel you. Arrows are arrows. Some have thicker walls than others and some have larger diameter than others. That doesn't mean that one is better than another. It's just how spine ratings are contrived and arrow weight determined. Just because the 22 series is 22/64" and thin walled just means it's faster than a similar shaft with thicker walls. It does not mean it can't be used for hunting.