The ALF-18 battery holder allows you to use an 18650 battery in flashlights that are built to use a 21700 battery. Simply insert your 18650 battery into the holder and place both into your 21700 capable flashlight. Made with copper plated contact, providing excellent conductivity performance. Compatible with button top as well as flat top 18650 batteries. Compatible with HT18, PD36R, TK16 V2.0, TK22 V2.0, TK22 UE. This will not work for the E35 V3.0 or PD40R V2.0. Compatible with button top as well as flat top 18650 batteries. Material: PC + ABS materials, copper plated positive contact. Size: 61,2 mm (Length) x 21,5 mm (Diameter). Weight: 6,1 g