Abstract: A parallelopiped is provided defining relatively isolated side-by-side alternate right angularly disposed passages extending therethrough and with the opposite ends of the first and second sets of corresponding passages opening through first and second pairs of opposite sides of the parallelopiped disposed between the third pair of opposite sides thereof. First and second pairs of tubular fittings including one set of corresponding ends of generally rectangular cross section have those ends secured to the first and second pairs of opposite sides of the parallelopiped with the corresponding ends of the passages opening into the rectangular cross section ends of the fittings.