Andersen Sash Balancer L8/1227

Based on that stamp, see our 24-L8-1227 Andersen balance. I believe this would be the one you are looking for. Take note if you are going to replace the balances on both sides of your window you will also need the 24-R12-827 balance. Take note these balances are left and right handed viewed from the outside of the house looking in.