he G&G UVT106-2.0 Tracer Unit (Newest 2021 - Version 2.0) is the smallest airsoft tracer unit we've ever seen. Built-in dual rechargeable 3.7v Li-Po battery. Illuminates a very bright UV light when it senses it firing. 14mm CCW fits on most airsoft guns with threads. Highly recommended tracer unit for airsoft! Made of Aluminum outer. Compatible with green tracer rounds only UVT106-2.0 Tracer Unit (2021 edition) NEW Upgraded Brigther UV LED Light with Quartz Lens Twice as bright as the 1.0 version Twice the battery power of the 1.0 version NEW Power Indicator Light Automatically Turns Off After 15 sec. Durable and lightweight aluminum alloy construction 14mm CCW Threads Powered by two 3.7V 180 mAh Li-Po batteries (built-in) Compatible with Green Tracer BBs Only Micro-USB Charging Port (cable not included) Did we mention it is bright? It's extremely bright! Dimensions: It's 51.5mm long and 27mm wide allowing it to fit inside most rail systems. Built-in battery charges on standard micro USB adapters.