Urparcel TrustFire TR-3T6 3800 Lumens LED Torch/Flashlight 18650 Battery Extension Tube Trustfire TR-3T6 3800 Lumens LED torch/Flashlight 18650 Battery Extension Tube Size (mm): 81mm (Length) x 20mm (Body diameter) For one more piece 18650 battery extension use. Trustfire Tr-1200, 3T6 and other models with same metal case design as follows, you are able to use 3X18650 INSTEAD OF 2x18650 batteries in your 1200 Torch.