Needed new Channel Balancers

I included a hand print of an old balancer. It looks like it might be your 28 series 351 channel. But the window sash is 20 lbs exact so it might be either the "2730" or the "2740" to cover the window weight. I live in AZ so these windows don't get opened so when I needed to, the window balancers kinda fell apart. I don't understand these seem to float in position. When I open the window they come apart again. The spring and cable systems are very tight since they are old. It allows the cable to come off the clip in the hole and when I open window they fall out. The window is exact dim on both ends as well as height. These are for a Jordan window. I also need instructions on how to assemble together please.

Hello,
The 15-002 being 1.00 and the 15-001 being 1-1/8....mine is 1-1/16. So which would work with mine being 1-1/16?. I agree with tbe 2740 and its better weight capacity as long as the channel size is the same obviously.. its at 1-1/16 now but it lookes like the corners have been worn. So it must be the S390 with 1-1/8