Earlier this year I contacted our wholesaler regarding the warranty procedure, and officially Knitter's Pride handles warranty claims (broken needles, cables, etc.). From what I was told you need to send the broken item to them. Personally, I'm not too keen on this. It puts too much burden on customer. Denise Needles, another brand we carry, will do replacements without such hassle. I think this is great and helps to build a strong brand and the way it should be.
Amy and I have decided to take on the burden and we extend a 1-year KH warranty for needles we sell. For people who order needles from our shop, we will replace any needles/cables that are received broken or breaks during normal use due to defect within the first year. After that, you can contact us and we'll try to help you out as best as we can. We can usually order a replacement needle, but if we can't you may have to go through the manufacturer for replacement. Most people discover any defects rather quickly and contact us within the first few months if they have a problem.
I'd expect most 3rd party amazon sellers to defer warranty replacement to the manufacturer. But we feel strongly in going the extra mile to ensure those who buy needles sets from our shop are happy and can keep on knitting and not to wait weeks for a replacement. So that's how we roll.