Sash pivot balance for a double hung window

Hi, I am looking for this balance pivot, I think it is called. It holds the spring of the sash and has a screw to tighten the tension of the window sliding on the sash. The pictures are the actual nylon part that holds the spring and the window pivots at the bottom of the window, for the bottom window and same configuration for the top window pivot to sash. I looked at every picture on your website pointing to balances and pivots and could not match this particular item. Thank you for your help, I am hopeful you can identify this so I can purchase them.