How much weight are you intending to lift?
Steel core belts require large pulleys or the wires in the core will break inside the belt and then the belt will stretch over the wires. That sort of thing has caused many hard to diagnose problems in 3D printers.
If this is for lifting a 3D printer bed, you don't need steel core belts. My printer has a belt lifted Z axis and I have tested the amount of stretch in both steel and glass core belts. Neither stretches enough to matter.
See: [
drmrehorst.blogspot.com]
I found that glass core belts stretch about 3x as much as steel core belts, but the worst case stretch in any one print layer on a 300x300 bed is 1.2 um for steel and 4 um for glass core belts, assuming that you are printing the entire bed surface with a 0.25 mm layer of PLA.
Ultra MegaMax Dominator 3D printer: [
drmrehorst.blogspot.com]