At the state level, all non-switchblade, non-balisong folding knives are legal, and CA has no legal length limit. Further, current law makes no mention of what materials the knife is made of.
However, there are two caveats:
1. Counties and cities in CA have their own rules on knives, for example in LA a knife cannot be more than 3" to be carried concealed. You'll have to look up your local laws.
2. Specific locations do not allow any type of knife, such as court houses, schools, airports and federal buildings. You get caught with a non-metallic like that and you are looking at a LONG prison sentence and potentially labeled a terrorist.
One last thing. I've got a few Zytel fixed blades and their really not that strong or sharp. You'd get maybe one solid hit before it dulls or breaks. And furthermore, the non-metallic angle I think is an underhanded marketing gimmick, because cops and many security used pat-down searches which will still find this knife.
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