Andersen string balance

No problem, we're happy to help! It looks like you have an Andersen cottage window which has a smaller top sash than bottom sash. So, you should go for the 24-L8-1227 and 24-R12-827. keep in mind, Andersen distinguishes left and right from the perspective of someone looking in from the outside of the house. Let me know if you have any other questions!