The cap gap or height question never seems to die.. Back in the day,Way back, the original pellet grill,Traeger did not have a cap on their chimneys...The sole reason for the cap was to keep the rain out..The cap solved the rain problem and generated an other.The bolt that mounts the cap has a full length thread that allowed the cap to be installed from its proper intended height to Zero height..Guidance was minimal to lacking re cap gap resulting in the cap gap being just about anywhere..When people reduced the gap with the the intention of holding the heat in* as on a wood stove, problems arose due to reduced air flow. Pellet pits have fans to generate air flow for efficient combustion. Conventional wood stoves don't..*.Holding the heat in was driven by a minimally sized and controlled burn system caused slow warm-up times. Low max temps in the cold and wind Etc.Thus the thermo blankets...Long winded I know. Hope you better understand cap gap now.