Question along the same lines, since I don't know what type of soil/dirt the topic starter has it may still be helpful to them...
Do people need to buy grit if they have free range or pastured poultry on sandy soil?
My local feed store says no... but I tend to trust more than one opinion.
And I think in some ways sizes are also up to the manufacturer.
Do people need to buy grit if they have free range or pastured poultry on sandy soil?

And I think in some ways sizes are also up to the manufacturer.