ACDelco 94011609 OE Oil Pump to Block Seal.
For 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016
GM 6.6L Duramax LB7 LLY LBZ LMM LML

Replacement O-ring on the back of the oil pump where it seals to the oil passage on the block.