Product review (3 stars): Decent design and construction
I installed this unit on a 5 degree pitched roof that was coated with torchdown.  There is a small drain opening (about 1/8 inch high all along the exit side) that appears to be designed to let any water that gets in the plenum area (between the 6" diameter tube and the rectangular housing) to drain out.  My roofer was very concerned about this drain slot (even though it was facing down the slope and the 6 inch diameter pipe is sealed to the base flashing) so he convinced me to put the torchdown material about 2" up all sides of the outside of the cap, thereby sealing the drain slot on the downhill side too.  He said if water can get in there, so can dirt and leaves and pine needles so it can clog up and cause an overflow back down the pipe.  I wasn't convinced but I let him do it - I figured I could always cut the torchdown that was in front of the drain slot if water got in and was blocked by the torchdown he put there.  Anyway it's rained pertty hard once and no water got in the house.  I found the 6" diameter stub on the bottom side of this cap to be a bit oversized however (about 1/4") so even putting my vent pipe inside the bottom and attaching with 3 self-tapping sheet metal screws, there was still a sizeable gap along one side so I had to use plenty of the foil tape.  Overall, if my roofer did a decent job, and my Panasonic FV-15VQL5 is beefy enough to force open the backdraft damper, I think this 6" diameter cap is one of the best designs available for pitched or flat roofs.