Nothing new, but first time I've used it.......duct seal. All I can say is, wow. It did wonders for midbass isolation in my doors. I recently changed my door mounted 6.5s out for 8s. With the 6s the doors, even though well sealed and damped, were still resonating pretty bad.....on quiet tracks with bass, the drivers door was irritating as hell. Now with tons more midbass, I can make it resonate, but it can be made to be fairly quiet. I was amazed at the improvement. After my door surgery, I made my hdp spacers, two per side.....I put a roll (think play-doh snake) in between the spacers, and then again between the spacers and door metal. I then surrounded the entire thing with about a pound of the stuff......like I said, wow, what a difference!