Do you have a 2015 or 2015.5 Duramax? 2015 was a split year for the GM Duramax. 2011-2015 the downpipe was attached the turbo-direct pipe using a v-band clamp. 2015.5-2016 the downpipe was attached using a 3 bolt flange. Before purchasing a new DPF delete exhaust system be sure to visually verify the clamp style your truck is equipped with.