A contractor from Merrimack, Nh says:
September 26, 2016
Do you have an overall size for this part from front to back? This same part has two sizes, one is about 7/8" from front to back and the other is about 11/16" from front to back. They both have the 1/4" leg that pushes into the sash.
Paul from SWISCO responded:
September 27, 2016
Hello! The overall width of our 55-186 is 13/16".