please help me find this part.

Thanks for posting. The part you are searching for is a top sash guide. It helps to guide the channel balance in the window channel and prevent it from shooting up into the frame.

Your particular guide is no longer made, unfortunately. We have suggested the 18-066 to other customers, however we cannot make any guarantees it would work as a replacement. Some sashes are made with a type of contour built into the framing that may not allow them to install properly on the sash.

With that said, take a look over the dimensions and design to see if you believe this could be a fit for you.

Front view of 18-066

Side view of 18-066