Specifications

Part number: B420 YS1300-4S-XS-US

Dimensions: 31 x 34 x 72 mm

Discharge connector: XT60

Balance connector: 5-pin JST-XH

Rated parameters
Dimensions	31 x 34 x 72mm
Continuous Discharge	91A
Capacity	1300mAh
Nominal Voltage	14.8V
Charge	<2C
Weight	155g

Derived parameters
Energy Capacity	19.24Wh
Energy Density	446.9J/g

Observed parameters
Dimensions	32 x 34 x 76mm
DC Internal Resistance	6mΩ
Capacity	~1200mAh

Photos

From the manufacturer:

Test Results

Continuous discharge:

Vaping profiles:

Observations

These packs seem to be under-rated in terms of capacity - it was not uncommon to get 1350 or 1375 mAh from them. They handled up to 10A discharge well, with no swelling and expected heating to ~30°C.