Please help me to identify this casement window part

This is a piece from my casement window. It is located on the right side of the window, and it assists the rail in moving up and down when I secure the window. There are three of these pieces and one of them is damaged. I hope this explanation is clear. I have not been able to find this piece and I need to know what it is called, so I can buy it.

Thank you,
Eric.