The tfs or The Frankenstein Series was built for Techforce to use in his expedition called Frankenstein hence the name. Rusty I dont believe has released them as a new series yet to do Techforce and a few other Team DBs members testing them in real world applications before they are released. To make sure they stand up to DC standards. But basically it uses an xl motor, lvl 5 soft parts I believe and it also has upgraded cooling, and the inverted dust cap. They are pretty nice woofers. I dont believe they like 4500 rms daily though just ask Techforce lol. In all very stout, strong woofers. Ready to take a good amount of power just like any other DC sub.