I am guessing those are 18" risers like everyone else, including me, uses.
It has been said that the elbows cut the air intake by as much as 50%. I do not have any issues with mine but on windy days, mine is pretty much a no go. I thought about loosing the risers and adding more exhaust to mine.
Mr. Bludawg, I believe it was him, has posted numerous times the math involved in figuring intake and exhaust.
If I could I would. If I don't, it's because I am to lazy!
UDS | Brinkman Gasser | Big Poppa Drum
On Deck: Weber OTG