How many cords do you get? The image shows 3, the description sounds like it could be 2 or 4.

You get 4 cords total, 2 in the 24" length & 2 in the 32" length. The set also works with the Knitter's Pride brand cords if you are looking for additional sizes.

Which cables will fit these needles? will knitters pride cables fit? the couplers, too?

Thank you for your inquiry. The cables that come in the set will only fit our needle tips. You can try to use them with another needle set but we can't guarantee that they will fit. This is the same with the couplers also. All accessories for the needles will interchange with our Caspian, Sunstruck, Nickel and Rainbow needles. Please give us a call t 1-800-574-1323 is you have any other questions. Thank you Knit Picks Customer Service

i need shorter cables

The 24" cable is the shortest cable available for the Interchangeable Needles. The tips are about 4.5" each, which takes up 9" of the cable. The tips would not be able to touch if we made a smaller cable. We did slightly shorten the needle tips and made a Fixed 16" in sizes 0-11 to compensate since we couldn't have a 16" cable for the Interchangeables.

What type of metal are the metal parts made of?

I cant say for sure as, I'm not familiar with different types of metal, but I'd say your common maybe nickel or aluminum, idk but its smooth and has a decent thickness to it, its not a flimsy set. its like hard metal tips. and the wood it smooth and solid feeling as well, I used to buy the metal ones from joann fabric but these are nice and less for an entire set so for that it was a nice deal.