I got a Turbo with the HSU I got a while back and I don't use it. I'm asking $125obo + shipping (It weights about 25lbs). I'm located at 79416 for local pickup and I prefer paypal or amazon payments. These were sold as an option to go with the VTF3 MK3 subwoofers, but the manual says they'll also work with the VTF2 MK3 woofers as well. I'm waiting to hear back from HSU's technical team as to where or not it benefits the MK4's. The idea behind it is to double the length of the ports to move more air. Here's a link to the user manual for it. Pics are below. The original owner put velcro on the bottom of it and to the top of the sub to keep them from moving apart. Seals seem good to me, but I never installed it. There are a few scratches on it from the previous owner, but nothing terrible. I tried to take pictures of the more obvious ones, the other scratches are in the textured black parts.