The 
Nuprol Power NiMH battery Deans single stick 9.6v 1600mAh
 is a reliable and durable power source primarily designed for airsoft electric guns (AEGs) with limited battery storage space. It is available for online purchase from several retailers. 
Product Specifications
 the battery has the following specifications: 
Voltage: 9.6 Volts
Capacity: 1600 mAh
Chemistry: Nickel-Metal Hydride (NiMH)
Configuration: Stick (single block)
Connector: Deans (T-plug)
Dimensions: 18 x 35 x 122 mm
Weight: 130 Grams
Recommended uses: Airsoft guns, drones, remote control vehicles 
 
Key Features and User Opinion
Safety and Charging: NiMH batteries are considered safer to charge than LiPo batteries as they do not typically require a fire-retardant bag during charging. However, they must be fully discharged before recharging to avoid damaging the capacity, and using a smart charger with an automatic cut-off is recommended for safety.
Performance: Users report that the 9.6V provides a noticeable improvement in an airsoft gun's firing rate and trigger response compared to lower voltage batteries like 8.4V versions.
Durability: The battery is described as a robust option that can withstand significant abuse compared to fragile LiPo counterparts.
Compatibility: The "stick" configuration is ideal for AEGs with long, thin battery compartments, such as certain AK models, MP5s, and some rear-wired airsoft replicas. Users should always check dimensions to ensure compatibility.
User Reviews: On Amazon UK, the product has a customer rating of 4.0 out of 5 stars based on a limited number of reviews, with users praising its performance and build quality.