4WD Long Travel Fox Spec Coilovers 2.0 Bump Standard collar fits 1-5/8" and

Standard collar fits 1-5/8" and 2-3/8" diameter necks

this is because your Duramax doesn't come with a factory System like other diesels

Year Make Model Submodel 1980-1989 Buick Electra Estate Wagon 1980-1985 Buick Electra Limited 1980-1985 Buick Electra Park Avenue 1985 Buick Electra T-Type 2004-2007 Buick Rainier CXL 2004-2005 Buick Rainier CXL Plus 1980-1987 Buick Regal Base 1982-1983 Buick Regal Estate Wagon 1987 Buick Regal GNX 1984-1987 Buick Regal Grand National 1980-1987 Buick Regal Limited 1982 Buick Regal Limited Turbo 1980-1982 Buick Regal Sport 1983-1986 Buick Regal T-Type 1999-2000

or hard-start condition

these will retain the OEM feature if the vehicles calibration allows and is setup for it

4WD Long Travel Fox Spec Coilovers 2.0 Bump Standard collar fits 1-5/8" andDescription The Dirt King spec coilover shocks were developed specifically for our 4WD F 150 long travel kits with a custom hose layout, custom valving, and proper spring rates. They are ready to be installed right out of the box. For the best off road performance we recommend pairing these spec coilover shocks with our spec bypass shocks. Specifications Shock Manufacture: Fox Spring Manufacture: Eibach Amount of Lift: Adjustable from 0 2. 5" of lift