The BZ400 is the gold standard for warm undergarments for cold water scuba diving. It's made with 400g thinsulate, but because of the excellent design, it does not restrict mobility. This is perfect to keep you warm during year-round diving, and will even retain heat when wet. This suit is used, and is custom fit. It's roughly a Medium Tall, and while it's perfect for someone around 180-200lbs and 5'11-6'3", it will likely fit you if you're roughly those dimensions (plus or minus 10-15lbs, plus or minus a few inches).
It currently has my name tape on it, but that can be removed. Priced at half of retail. Item is used. The undergarment has a small tear in the mesh at one wrist, and minor wear and tear throughout. Nothing immediately concerning, and it should have plenty of use left in it.