TWC0006 is a crossflow charge air cooler for Western Star trucks.
The core measures 34" high by 21" wide, 2.8125" deep. It has a 4" inlet at the left and a 4" outlet at the right. There is no integral oil cooler and no filler neck.
It replaces 38 OEM and aftermarket numbers, among them WES18201, WES18201ED, WES18201N. Searching any one of them will find this part.
On charge air coolers the inlet and outlet positions and the boot diameters matter as much as the core. A cooler that fits the opening but presents its connections on the wrong side will not plumb up.