A handy person from Tarpon Springs, Fl says:
April 13, 2016
First bracket is stamped 2830. The cylinder bracket measures 16 inches.
Paul from SWISCO responded:
April 15, 2016
Looks like you need two different balances, a spiral balance and a channel balance. For the spiral balance, start with our Series 900, which has an outer tube diameter of 3/8". You may want to check to make sure this is correct. For the channel balance, consider our Series 390 instead. Again, carefully compare our measurements and pictures to your own hardware in order to confirm.