Back when the Terminator was first released there weren't a lot of CAI's available. K&N released one of the first, and in my opinion still one of the best. The original non-C.A.R.B. certified FIPK they released came with a solid aluminum velocity bell. If you look at the picture in my Garage you can see it. Basically it's a velocity stack which the filter mounts to. This creates a vortex as the air enters the MAF. Those of us who purchased the FIPK and then dyno'ed their cars were seeing gains as high as 15 RWHP from this mod alone! We nick named that aluminum velocity bell.... THE MAGICAL VELOCITY DONUT! The new FIPK's still come with the velocity bell, but it's made of black plastic now.