fixing a hard to slide window

I wish I knew the correct window style that we have... I guess they would be called slider windows, one half of the window slides horizonatally to open. They are very heavy and the track which the window slides in doesn't allow the window to open very easily.
A neighbor showed me how one of his windows was repaired (they are the same brand/style of window). It looked like a strip of composite-graphite or carbon had been placed in the bottom metal track that the window slides on. Possibly something had also been attached to the bottom of the half-window as well. It slid amazingly nicely.
This did not look like a particularly difficult fix. Can anyone point me to products like what I just described?
regards, -jsb
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