How to change the density of a demo model?

Hi, I am trying to understand a SimMechanics demo. When the demo is loaded, a .m file which stores the values for some parameters are loaded. There is a section at the top of the file which defines the Material Properties. It states: density = simmechanics.demohelpers.densities;

When I double clicked a Solid in the model, under Inertia it states that it is based on the Density and the Density is rho. I cannot find rho being defined in the .m file.

Please let me know how to change the density to aluminum.