an official Valve product. You cannot activate a "Carbon" key on to get a legitimate copy of the game. Why You Should Be Cautious
Built on a "Carbon-tuned" version of the GoldSrc engine, providing maximum FPS and minimal input lag, making it perfect for competitive play on any PC or laptop. Counter Strike Carbon Cd Key
Given that Carbon was a free mod , the only reason it needed a CD key was to prevent piracy of the Half-Life 1 engine or to track online rankings on specific modded servers. Today, 99% of websites claiming to sell a "Premium Counter-Strike Carbon Key" are phishing scams. They will take your $5 and send you a random string of numbers that will not work. an official Valve product