I'm a fairly new user to PyMol and am having some trouble with the sphere_scale command. I understand that if I want to draw a sphere around the x'th ca atom, I can use:

show spheres, ////X/ca

However, what if I want that sphere to have a radius of 3 angstroms, or 6 angstroms, etc.

 I understand I can use set sphere_scale, 1, ///X/ca but what is the default scale of 1? Is it 1A, is it something else?

Thank you for your help!

Kind regards,