This is a ProTek R/C "Supreme Power" 2S 5500mAh, 35C hard case LiPo battery pack. This battery is built using a hard plastic case that is required for use at ROAR sanctioned tracks and events. The packs are thin enough to fit into all touring cars and off-road vehicles and can be used in any application where you need 6-cell NiMH stick or race packs. These packs are significantly lighter when compared to regular NiMH race packs for significantly improved acceleration and have dramatically reduced internal resistance. This leads to increased top speed and improved 'punch' off the line when compared to NiMH batteries.