DISCONTINUED: Bilt Well Casement Operator with Large 7/8 inch round nylon button, 10-1/2 Straight Arm measured from the center of the operator to the center of the button.
The replacement operator has a smaller nylon button and requires changing the operator and metal track on window sash.
Note: 10-1/2 inch straight arm is replaced with a 9-1/2 inch arm.

Bilt Well Replacement Operator Hardware:
55031 - Left hand Traditional operator with 9-1/2 inch arm ( Discontinued Limited Quantities)
55160 - 11-3/8 track with 4 screw holes 
55311 - Handle, if needed 

NOTE: 1
When Traditional styles are no longer available the operator may be replaced with Truth discontinued styles Ellipse, Nested or Maxim Series ( Limited Inventory)

NOTE: 2
Current replacement would be the Encore Series that uses a folding handle and cover with new track.
52.11.00.211 Encore Straight Arm Operator, LH
55309 Folding handle and Cover
55104 Track and Slide Guide