Need channel balances for older window

A contractor from Columbia md says:
Trying to identify the proper channel balance for replacement. My current balance is stamped with 18D. So it looks like I need a 19": Series 371 seems to be closest but may not be exact. The bottom plastic piece is likely 15-005 (those measurements are the same as my existing piece), but I am having trouble identifying the top plastic piece. 19-031 doesn't match my existing piece exactly. My top piece is 15/16" wide and the tabs are 3/8" tall.

Thanks for any help,
User submitted photos of a window balance.
Profile picture of Paul
Paul from SWISCO responded:
Thanks for posting! There's a good method of confirming whether our Series 371 can work for you or not. Take a look at your top sash guides. If they look like our 18-124P, then you should be good to go. These are for Rollyson windows, which is what our Series 371 is made for.
Reply to Thread
Use this form to ask a follow-up question or to share your experience regarding this subject.
(your email address will be kept private and is only used to inform you when a response has been made)