Silverline Window Broken Part Identification

A home owner from Indiana says:
I have several 400 Series Silverline windows (crank) where the middle black piece that attaches the arms to the window are broken. It makes opening and closing the window difficult. The crank arms fall off the track. What is this black middle piece called?
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Bob from SWISCO responded:

That nylon piece might be part of a bracket like our 39-340 or 39-424 . These are used along with our 39-393 , which looks fairly similar to yours. Please compare to confirm. 

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