When playing extended range guitars you pretty much need active pickups to get the clarity required. EMG's were the first and are the best in this department. An active pickup means that there is a built in preamp that run on a battery in the pickup. EMG was one of the first companies to make active pickups for extended range guitars. Since they were the first they were making them before there was a standard for 7 string pickups so they are not the standard size. If you trying to put these pickups in a guitar that didn't come with EMG's originally you will have to do some cutting. This is the 707TW. The TW is important because it means you can split the coils of the pickup. This is a rare feature in active pickups because it pretty much means that there are two pickups in this pickup. You cant really split active pickups. On this pickup there is the regular 707 pickup and there is an EMG SA along with it that you can switch between. The EMG 707 is like an slightly tweaked 85 for the 7 string. The 85 is an ideal choice for a 7 string guitar because it naturally has a thicker sound than the 81 and it more naturally plays up the low end frequencies of the guitar. If you are playing 7 or 8 string guitar you are not looking for a thin sound so naturally you want to retain the thick sound but also want to have some clarity with it. The sound in single coil mode is fat as well but still has the single coil twang to it. This is a great setup if you want more versatility of your active pickup guitar. If you have a 7 string guitar with EMG's and want the versatility coil splitting adds the 707tw is a good substitute to true coil splitting.