Turn your 21700 DD into a single tube device!
>>> Step 1: Tighten Battle Deck onto DDiesel, set aside.
>>> Step 2: Thread button housing onto DoubleDouble device, then insert battery- positive side up.
>>> Step 3: Place DoubleDouble Contact on top of battery.
>>> Step 4: Thread DDiesel top onto DoubleDouble and adjust housing for battery rattle.
Donut contact required for use, sold separately.