The 191X65-8 is a 8.0Ah Battery BL4080F.

This is a High Output battery, built for high-demand XGT tools such as chainsaws, breakers and demolition hammers. Compared to the standard equivalent-capacity battery, it delivers up to 35% more continuous power thanks to high-performance cells with lower internal resistance, allowing much higher peak currents. It also runs up to 32% cooler under sustained heavy load, so it can go straight back on charge without needing a cool-down period, giving noticeably better runtime and performance on tools that draw hard current during cutting, grinding or drilling.