truth casement arm

We should be able to help with this operator. Before I recommend anything, can you disconnect the long, straight arm from the track and show me a picture of its end?

That detail is important. There are a couple different operators that match this style, but they differ in how the arm slides in the track. See our 39-439B and 39-253RB for the two types we carry. We also sell the 39-452 cover separately. The video below will go into more detail as to the differences between them. You'll need to figure out which type you have before you place an order.