This is an E-flite 1S, 25C, 150mAh Li-Poly Battery Pack. This battery is used with the Blade mSR, Nano CP X, mCX and mCX2 helicopters, as well as the E-flite UMX ASK-21, HobbyZone Champ, and ParkZone Ultra Micro P-51, J-3 Cub, Sukhoi, Ember, Night Vapor, Pole Car, T-28 Trojan, and Spitfire airplanes.

Specifications:
Type: LiPo
Capacity: 150mAh
Voltage: 3.7V
Weight: 0.14 oz (4.15 g)
Configuration: 1S
Length: 1.47 in (37.5mm)
Width: 0.48 in (12.2mm)
Height: 0.22 in (5.5mm)
Maximum Continuous Discharge: 25C
Maximum Continuous Current: 3.75A