THIS IS AN ALUMINUM 4X4 EXTENSION HOUSING USED IN THE LATER MODEL 4L80E TRANSMISSIONS. THIS HOUSING WILL REPLACE THE EARLIER CAST IRON EXT. HOUSING'S.THE CASTING NUMBER IS #15724745. THIS HOUSING WILL FIT EARLIER 4L80E'S. THIS HOUSING ALSO COMES WITH A NEW O-RING AND GASKET TO SEAL TO YOUR TRANSFER CASE AND ALSO YOUR TRANSMISSION. THIS HOUSING MEASURES 2 1/2 INCHES. THESE HOUSING HAVE BEEN CHECKED FOR CRACKS,AND CLEANED.THE MOUNTING BOLT HOLES FOR THE MOUNT HAVE BEEN CLEANED AND CHECKED GOOD.                                                                                                                                                                                                                                                                                                                                                                                                        YOU WILL RECEIVE: