What is a pivot shoe bumper? Do I need it?

A home owner from Sugar Land, TX says:
I have sash windows that use S160 Series coils. Will be replacing several in my house. I also see a product listed as Bumper, Product Code: 15-148, that I am not sure what is for and whether I will need it. Could you tell me its purpose, where it's located, and whether I should replace it as well while I'll have the windows' sashes taken out.
Thank you,

Andre
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Bob from SWISCO responded:

Hi Andre. Good question. The 15-148 Bumper sits between the pivot shoe, such as the 15-111 or 15-191, and the coil support holding the Series 160 Coil Spring(s), such as our 15-150S. Every Coil Balance system has unique idiosyncrasies in design; in this case, the 15-148 just acts as a literal 'bumper' between the pivot shoe and coil spring & housing, enabling support and so that the coil springs don't slide too hard into the pivot shoes during window operation. 

A home owner from Sugar Land, TX says:
Thank you, Bob. The bumper on the photo has 2 legs on top. I assume they are there to attach it to something. Could you, please, clarify whether the bumper legs are inserted into the top of the shoe which has 2 holes, or (somehow?) into the bottom of the spring housing.
Thanks!
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Tom from SWISCO responded:

The 15-148 bumper installs on the bottom of a cover like the 15-150S. See the image below from an older discussion for an example of what I mean. If you never had the 15-148 to begin with then I wouldn't worry about it.

Example of how a pivot shoe bumper works.
A home owner from Sugar Land, TX says:
Thank you! A picture is worth a thousand words :)
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Tom from SWISCO responded:

My pleasure! Let me know if you have any more questions and we'll do our best to help.

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