This is the two to six cell lithium polymer balance connector from Align. This Y-connecter is attached to your lithium polymer battery and to the Thunder Power TP210V 2-10 Cell Li-Poly Balancer to equally balance each cell in the pack while charging. Although this adapter is designed for 6-cell batteries, you can also use it for any number of cells from 2 cells up to 6 cells, simply by making sure you plug in the smaller number of cells lined up with the black balance lead. So this will also work great to balance 3-cell Align batteries used for the T-Rex 450 helicopters.