It is a split vertical core, each side is 6" x 12" x 4.5". the charge face being 12" (number of tubes)x 4.5"(thickness) and the tube length being 6" I think it solves the pressure drop issue, as well as issue of the fascia blocking airflow to the top bank of a horizontal fmic. I should have the bulk of the work of the install (and pipemaking) done this weekend ;)