What do you call these window balancers?

My windows have a "lead screw" on each side that is supposed to keep the windows opened. Problem is that most of them have fallen out the bottom of the window, or they are not working properly. There are no names on the windows, so I can't go to the company's web site for assistance.
Does anyone know what these balancers are called so I can do a google search?
Thanks.
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

http://www.blainewindow.com
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.