I 'd like to inform a bit here the newbies about this setting cause I know it would be a kind of confusing how to use it and it really can help with false signals and effects the smallest targets to be detected rather from being masked from cold rocks. HRR it is very helpful when used in a moderate ground or high in minerals ground. The detector Simply cease from responding to those minerals that gives you a headache especially when hunting for such as tiny targets as gold jewelery and not only. Hot rock is called the one that is above your ground balance and cold rock is lower than the GB So finding the right setting according my experience for your field makes you keeper at end of the day.