Can anyone tell me what the difference is between the cold card and other air gapped devices. I dont really get it. It has a secure element just like some others. I have currently a trezor and a ledger where I am considering a cold card, but dont understand why owning one is better than the other two. Secondly, When you go to the coinkite store to purchase 1 cold card, does it come with the cable, power adapter, and SD card? Or do you have to purchase those separately? The site is not clear. Thanks