2030 but can't tell which part... you have too many!
A handy person from Santa Cruz, CA says:
October 6, 2016
I wish you have a comparison matrix or something to help us non-professional folks see the difference between all your parts! My part is 21" long.
Tom from SWISCO responded:
October 10, 2016
Hey, Ed! The major difference between channel balances of this type is determined by the nylon attachments they use at either end. We have detailed dimensions for all of our hardware you can use as reference. In your case, this could be either our Series 380 (which uses the 19-005 and 15-005) or the Series 385 (which uses the 19-005 and 15-004). Look this hardware over and see what you think.