Picking the right airsoft battery may be tough. Nimh batteries are the most common, typically in 9.6v and 8.4v configurations. Lipo batteries are becoming more popular. Normal airsoft guns without a MOSFET can use 7.4v batteries. 11.1 Lipos should only be used with guns with MOSFETs. Li-Ion batteries are similar to Lipo batteries except they are smaller and last longer than lipos. The higher the voltage the higher the rate of fire you can achieve.
The mAh is the milliampere capacity that each battery pack has. Each mAh is comparable to 2 -3 bbs shot, meaning that if a battery has 1000mAh, you should be able to get 2000-3000rds through the airsoft gun before the battery dies. At MiR Tactical, carry high-quality batteries from brands like Elite Force, Valken, ASG, and more. You can also find chargers, battery boxes, and accessories for your batteries.