Looking for recommendations for bottom and top roller material for use with the cheap 600mm 25mm exercise bands.?

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thanks?

Not cheap and prone to creep but Teflon is basically the best negative source (pvc will also work great) and nylon66 or nylon 6.6 is I think the easiest and best positive source. You really need nylon 66 and not nylon 6,nylon 6 will not work. You can test for nylon 66 because it has a higher melt temperature compared to nylon 6. Also you may need to turn on a lathe or sand the outer edge/diameter/circumference of the raw round stock because the surface could be contaminated with something from extruding the material (as I found out on my stuff)?

The for me famous Richard (Dick) Linder used the Teflon nylon combo if memory serves me well

As a side note avoid anything black because it is likely to contain carbon or graphite which conducts electricity pretty well at high voltages