TWR0013 is a downflow radiator for the Western Star 4900, model years 2008 to 2011.
The core measures 42" high by 41.625" wide, 2.25" deep. It has a 2.5" inlet at the top right and a 2.5" outlet at the bottom right. The unit carries an oil cooler at the bottom and no filler neck.
It replaces 35 OEM and aftermarket numbers, among them WES25, 0526876002, 0526876006. Searching any one of them will find this part.
On radiators the inlet and outlet positions, and whether the unit carries an oil cooler, decide interchangeability more often than core size does. Two radiators with identical cores are frequently not interchangeable.
