Window rollersI think they are Renaissance windows.

A handy person says:
Window Rollers
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Bob from SWISCO responded:

Thanks for writing in. This is called a coil balance system. See our 15-102 Double Side Carrier. This works with our Series 145 Coil Balance springs, sold separately. Look for stamp codes along with the coil springs to figure out what spring weights you need. If there are none, or you are uncertain, give us the exact weight of your window sash, and we'll figure out what you need. Many thanks.

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Paul from SWISCO responded:

The parts you are inquiring about are actually coil springs and the housing. It's what helps the window go up and down. For the carrier, the 15-102 will work. The Series 145 coil springs that go with this part are sold separately. Take a look and let us know if you have any further questions. 

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