6' 5" - 300 pound, the 3XL jackets fit me perfectly (54L sport coat). I wear the 40 waist pants. They just started offering some of the peloton fleece in 3XL, so haven't been able to try any of that yet. Don't have any Sitka, but do have Kryptek and sizing is very similar. I wear an XXL in Columbia PFG shirts (XL Tall when I can find it).