The manual states exhaust for P68 is 3". It's actually 3 & 3/8" as I just found out after picking up my stove today. So the duravent pvp adapter cleanout tee I ordered for the stove has to go back. I was wanting to kill two birds with one stone using an adapter tee, but now I'll need two different expensive parts to go straight up right out of the back of the stove. What a racket... And why couldn't Harman just publish the actual exhaust diameter?