identify which balance

spiral balances for tilt alum secondary double glazing.
weight of sash is 11kg
length of tube is 34.7/8 inches
dia of tube is 9/16 or 5/8 according to your website
sash windows have fixed horns which home into flat slot.
I make a guess that these are not original due to 2 animalities 1 screw and stop at top of window had silicon sealant, this may be simply to hold the plastic stop in place and 2 tube was in channel with double sided tape