The dimensions of the top sash channel balance guide are: 5/8 inch wide, and 2 3/16 long. The depths vary; on the top it's 9/16, on the bottom it's 3/8. I don't see it in your inventory online.
Dave Sr. from SWISCO responded:
July 30, 2019
Take a look at the 18-008 top sash guide to see if the dimensions match up to yours.