Thanks for posting. See the 24-R18-1027 Andersen Sash Balance. This balance can replace old Andersen balance boxes with the stamp 'R18-1027'. Bear in mind this particular balance is meant only for the right-hand side of the window. For the left-handed side, see either the 24-L10-1827 or 24-L12-1827; check the stamps on that balance to verify which you need. Let us know if you have any questions.
This should be replaceable with the 24-L10-1827, since the balance has that same stamp. I should clarify that Andersen left and right handed orientation is judged from the outside looking in; hence the confusion. Either way, simply use the 24-R18-1027 and 24-L10-1827 to replace the balances with those exact stamps from the respective side of the sash they came from, and you should be good to go. Let me know if you have further questions.
