XO Seven are nearly identical to the XO Fours. In fact, if you have an adapter piece that plugs into the controller they are basically XO Sevens. Let me try to explain: The XO Four [b]headset[/b] is essentially the same thing as the XO Seven [b]headset[/b]. The only major difference is their adapter pieces. With the XO Four's adapter piece, you can mute your mic, adjust volume and chat (but they're linked. By making one go higher, it makes the other decrease by a bit). The XO Seven adapter is the same as the XO One adapter (the cheapest XO headset I believe). This adapter includes all the features from XO Four's adapter as well as others. It has independent chat and game volume (So you can have both super loud if you wish). Bass boost which can be turned on or off (!! Yay!) and you can hear yourself when you talk which is actually a good thing with these types of noise reducing headsets. So basically this is what I'm saying: Almost every feature of XO headsets (and maybe others) has to do with that little adapter piece that you plug into the Xbox controller. There is almost no difference between the XO Seven headset and an XO Four that is using an XO One (or XO Seven) adapter. While I don't know the prices of each, check them! Honestly, it might be cheaper to buy the XO Four new and find an XO One off of eBay and just use the adapter from it.