This spacer fits the 2011+ LML Duramax engine, if you have a 2001-2010 Duramax click here
Its a tight fit to squeeze a filter wrench around the fuel filter with the newer longer filters. GM designed a step in the bottom of the can to help with the problem, but its still very tight, especially with the wires routed close to it.
After being frustrated with this, We developed a rather simple solution to the problem, a 3/8" thick aluminum spacer to move the filter head away from the valve cover. This is enough room to make getting a filter wrench in there a lot easier, but not enough that it makes it tough to get the filter out of the engine bay. We include two bolts that are longer to support use of the spacer. Install is very easy. Simply take out the two bolts that hold the filter head to the support bracket and install spacer and longer bolts. No fuel lines or wires need to be moved or extended.