I believe by 43%, they're talking about what Zytel is made of - if I remember correctly, it's 43% glass, 57% nylon.
The CAT is undetectable by metal detectors (at least all the ones I know of). However, as a knife, it's just about completely worthless - I've had one for about 3 months.
Don't get me wrong, the CAT is a fun toy, but you really can't use it as a knife. They don't come razor sharp, and you pretty much won't be able to get them to anything resembling "sharp." Using a nail file (the recommended way to sharpen them) I once got it sharp enough to cut rolled up newspaper. (the edge didn't last long)
As a tool, it's useless. As a weapon, it might be somewhat effective as a stabbing implement. If you want a smaller, more effective weapon made of zytel, get a CS Delta Dart - very small, very cheap, made of zytel, and probably very effective. I believe Smoky Mountain knifeworks (
www.eknifeworks.com) still has them for $1.99each + shipping. The neck sheaths for the delta darts run $3.99, I think. Kind of fun, and a definite novelty item.
X-ray machines could definitely see the shadow of either knife. Think seriously before carrying one of these into a secure area, as for starters, it's probably illegal, and secondly, there's probably a reason it's a secure area. Also, zytel knives are completely illegal in Cali. I'm not sure about other states.
For better quality, you might want to consider one of the G10 or Carbon fiber knives made by a number of manufacturers. The cost is significantly more, but worth it (easily $60). Do a search for "non-metallic knives" or the like in the forums, and you'll get lots of hits.
-- Rob