This is the Billet Block and U-Bolt combination included with Carli 2.5″ Leveling system. This is NOT compatible with the Auto-Leveling Air Assist Trucks. CS-DRBKIT-1-4.25 1″ Billet Block pairs perfectly with 2.5″ Leveling Systems Includes U-Bolts Fitment: 2019+ Ram 3500 4×4, With 4.25″ Axle Tube Will NOT fit 2019+ 3500 with Factory Air-Assist