Yes it does what it says it will and when at a rally or the race track it's a must. I tried making one out of 2" PVC and this metal 90 degree sweep BUT in hot weather the PVC got hot enough to bend. For one night I'll just use the sweep to make the hot air go up or forward depending on the wind.
So, I GOT CARRIED AWAY and spent $15 on this one. I made it out of alum 2"X4" gutter down spout and a 90 degree elbow. Already designed to slip together and cutting the 10' into two 5' is easy enough plus it makes it easy to store. 10' gets it above the roof.
By having this large of a air gap it lower the temp of the up pipe by 15 degrees to 120F.
The 4" suction cup came from Harbour Freight ($4) plus I had the white channel that slips into the joint. Not that it weighs all that much but the suction cup will support all the weight so it's not going to hurt the gen exhaust.
Putting a little paint on the two joints helps in putting it together. Just made another one for a friend and it cost $17. Today it may cost $20.