An ARIA slider exposes its min, max, and current value, but no step size. Indie UI provides a way to change the value, but even absent that it might be valuable for assistive technology to know the plausible step size that's allowed when changing a range value.

Note that <input type=range> already supports a step attribute.

I propose aria-valuestep

Example:

<div role="slider" tabindex=0 aria-valuemin=0 aria-valuemax=100 aria-valuestep=10 aria-value=70>70%</div>