This key is not available in the following countries: RU, KG, MD, AM, UZ, JP, GE, TM, TJ, KZ, AZ, UA, BY. If the person you're gifting this to lives in one of them, Steam might prevent the key from being redeemed.

https://www.steamgifts.com/giveaway/xFJZt/killing-floor-the-chickenator-pack