window channel balance for vinyl single hung non tilt window

Need window channel balance for two different sash weights. First channel balance is for a 20 pound sash weight, measures 27" long, 1/2" channel width, with a stamp of 26 4 KW CMC 7. Second channel balance is for a 13.5 pound sash weight, measures 27" long, 1/2" width,with a stamp of 26 4 AX CMC 7. Both are block and tackle style and resemble picture of 380 series. window frame channel measures 7/8"-1" wide.