This is a Li-Poly 2300mAh transmitter battery pack from ProTek R/C that fits the Futaba 3PK and Airtronics M11 transmitters. This light weight Li-Poly transmitter battery is designed to reduce the overall weight of your transmitter, which is great for those long main events! The overall weight of your transmitter will be significantly reduced over the use of typical NiMh receiver packs. (138 grams compared to 225 grams for eight typical NiMH AA batteries!). Try to hold a pack of eight traditional AA size batteries and compare it with this Li-Poly Transmitter pack. The feeling is just awesome, and you get an incredible 7 to 8 hours of run time! Runtime: Don’t be thrown off by the capacity rating of Li-Poly battery packs, as you will get awesome runtime out this pack! Given that Li-Poly battery packs provide a higher nominal voltage (11.1V nominal), the actual capacity of the battery pack when compared to a typical NiMH battery pack (9.6V nominal) is about 15% more than the rated value (so this pack would be about the same as a 2600mAh NiMH pack in total capacity). How should the battery be inserted into the transmitter? A suitable foam should be used to pad the battery in the transmitter battery compartment to prevent the battery from moving around. Place a piece similar in size to the battery into the transmitter battery housing under the battery, and then while pressing lightly on the battery, slide the cover over the battery. IMPORTANT: 1) You will need a Li-Poly specific charger to charge the pack (NiMH or NiCD only chargers WILL NOT WORK!) 2) You must not over discharge the Li-Poly battery pack below 9.0V. 3) Read the instructions carefully before operating this battery.