Block-and-tackle channel balance replacement - 33.5? non-tilt aluminum window

Question

I am looking to replace a pair of block-and-tackle (channel) window balances from a non-tilt aluminum single/double-hung window.
Details:

Balance type: Block-and-tackle / channel balance (non-tilt)

Stamped marking (partially visible): “33.5 JT CMC 2”

Metal channel length: approximately 33.5 inches

Window sash weight: approximately ≈ 28.5 lb

Quantity needed: 2 balances (left and right)

Application: Aluminum window, sash does not tilt inward

The existing balances have dual internal springs and nylon end shoes. The window sash will not stay up due to failed balances, and both sides need replacement. I am looking for a compatible replacement with the correct length and weight rating (approx. 15–35 lb per balance).
Photos of the original balances (installed and removed) are attached.

Bob · Accepted Answer

Hello there. Can you double-check the metal channel length (not including the plastic end attachments)? Usually for a balance like this we'd expect an even length metal channel of 34". But please confirm.