This Western Star aluminum core, plastic tank radiator, fits 1998,1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 4900EX , 4964EX, LOW MAX. Core Size: 38 x 34 1/2 x 2 3/16 The service part radiator is now aluminum instead of copper brass. The core has been changed to aluminum in order to accommodate the higher horsepower applications. On the copper brass radiator there are two support rods on the front and back sides of the radiator that run form top of the radiator to the bottom for added strength. The aluminum radiators do not require these four support rods so DO NOT attempt to transfer the support rods from the old radiator to the new radiator. Doing so will cause interference in mounting. When installing the aluminum radiator IT IS IMPORTANT TO REPLACE THE FOUR RUBBER ISOLATORS that go between the radiator and the frame.