Nickel Metal Hydride (NiMH) batteries are your best bet when it comes to a durable battery that's going to last. Less sensitive than a Lipo battery and not susceptible to battery life memory loss like Nickel Cadmium battery packs; NiMH batteries offer the best of both worlds. Great for entry to mid-level players who just want to enjoy the game without having to worry about their batteries. The butterfly configuration is specifically designed for use with stocks where each of the two battery sticks are inserted into separate stock tubes. However, butterfly batteries can also be used in many other airsoft AEGs that feature varying battery storage areas inside the gun. If you're new to airsoft and need a battery to power your brand new gun, this is probably your best option! We always recommend a spare!