What is one of the differences between MINIMUM -security prisons and LOW-security prisons?

Low-security prisons offer inmates furloughs, but minimum-security prisons do not.
Low-security prisons have a lower staff-to-inmate ratio than minimum-security prisons.
Low-security prisons have double fencing around the perimeter, and minimum-security prisons have single fencing.
Low-security prisons use dormitory style housing while minimum-security prisons use individual cells.