Distinctive insignia of the US Army Corps of Engineers.
Refer to DA PAM 670-1 Chapter 21 regarding Regimental Distinctive Unit insignia for instructions on wear.
21–23. Regimental distinctive insignia
a. Authorization. Soldiers wear RDI when affiliated with a regiment or whole-branch regiment (based on a Soldier’s branch, corps, or special branch as determined by PMOS or specialty).