Question

If two items have the same mass, why would their density would be different?

Answer 1

Remember, density is defined as some amount of mass per unit volume.

So if the mass is the same for two objects, their volumes must be different in order for their densities to be different.

Answer 2

Pompeii00 is right.
Also, whenever you are asked about density, always think for density of the material of which the object is made OR the density of the object itself.