A "Red Devil" in LE and Mil explosive breaching refers to a 12" piece of Detonating Cord with a blasting cap and  junction clip attached. This is used to "tie in" to your full size charge. Although this is old school and has since been replaced with better quick detach options, it has a special place in a breacher's heart.
 
 
All Soileater T-Shirts are Next Level Apparel CVC Crew: 60% Combed Ring-Spun Cotton 40% Polyester. Shown above is a size: Large on a 6'3" 200 lbs model.