The XTAR MC4 charger is the perfect light weight on the go dual bay USB charger, perfect for your mods 18650's and 21700 batteries, as well as many other sizes, full list below.  It can charge x4 batteries on the go at the same time. It has all the features you would expect from the leading name in this industry.

Features:

• Charge current of 1 Amp (two ports) or 0.5 Amps (all ports).
• LED indicators to display recharging progress.
• Designed to recharge 3.6/3.7V Li-ion, IMR, INR and ICR specialist battery sizes, as well as codes 10440, 14500, 14650, 16340, 17335, 17500, 17670, 18350, 18490, 18500, 18650, 18700, 20700, 21700, 22650, 25500 and 26650.
• Can recharge two 26650 cells (in CH1 and CH4) plus two unprotected type 21700 simultaneously in channels 2 and 3. Not designed for use with protected type 20700 and 21700 cells.
• 0V activation feature to revive flat batteries.
• Automatically monitors performance and restricts any temperature increase to a maximum of 15° Centigrade. Reverse polarity and short circuit detection.
• Manufactured from robust, flame-retardant material.
• Dimensions: 100 x 97 x 26.5 millimetres. Weight: 94 grammes.
• Convenient to use worldwide.