I ordered one Yubikey and 2 covers Within 10 minutes of ordering, I got a phone call verifying my purchase because the covers are not interchangeable and they thought I might have made a mistake with my order (less scrupulous companies would have just accepted the extra money had the order been incompatible) I explained that I had purchased a Yubikey some months back and that the extra cover ordered was for the previous key. I had used a different email address hence the order confusion Not only was the order verified but they on the spot offered to merge the email addresses to avoid future confusion! Talk about attention to detail I paid the extra for express delivery and the order was delivered the next day - impressive!