This is a required purchase if you bought the Monster Cable VGA cable or component cable for the 360 and you want digital audio. They have a custom jack on the side of their component or VGA cable that requires an adapter unlike the Microsoft ones that have a standard Toslink jack. Buying their optical cable is only way to buy the adapter. Fortunately the prices are reasonable and for the price of a standard cable you get the adapter jack for free. Basically its a way for them to make more money off of you because there really is not a necessity for this. Its rumored that the older adapter that comes with Toslink cable for the original Xbox also works with this jack.