Hallmark window channel balances, 27 4 BSI

All the windows in my house are Hallmark brand. Need the part that supports the window when opened. The plastic end pieces are broken. Mental rid is about 38 inches. Any assistance is appreciated.The number on rod is 27 4 Bsl. The letters couldnt be seem with the naked eye, the best I can tell. The window measures 35 width by 59 length. All of windows are Hallmark brand. I seem to have the problem with the rods not staying in place causing window to drop down.

If this is the right part, may needs a few. Is there any thing written on how to maintain this hardware to prevent from breaking?

I think he is asking about the sash corners that hold the balancers. It's my experience that ,that is the weak link on those windows. The plastic corners that hold the balancer to the operable sash.