Red Engine Oil Filter Cooler/Heat Sink Cover/Cap Billet Aluminum Kit Ef Eg for Dodge Dart Each Fin / Heatsink is 9.81mm deep (.3 inches). Lower engine oil temperature's mean longer engine life. Overall outside diameter of the heatsink is 101.6mm (4inches). Adjustable size from 73mm (2 3/4 inches) to 76.3mm (3inch) diameter. Made from weapons grade billet aluminum to withstand the test of time.