Li-Poly 2100mAh 7.4V battery extends your transmitter operation time by almost 100%. No more problems with self discharge, charge only about once per month. Li-Poly transmitter battery pack discharges only by 4% per year. Always remove from transmitter case while charging. Included: (1) TP2100 2S battery pack (1) 1/2” x 10” (12.5 x 255mm) Velco Strip (1) Deans Micro 2-Pin polarized connector (1) 2” x 1/2” (50 x 12mm) Self-Adhesive Velcro "loop"