Consultation Fee Slider

I noticed in the dDoctors demo page, there is a Consultation Fee slider for filters in the All Listings page. In fact, I even see this slider in the dLawyers demo page (here it’s called Pricing).

I have added a Pricing field for my Directorist-based listings with dDoctors theme, and have even enabled the range, but when I go to the All Listings page, in the filters I only see fields for min/max and then 4 different buttons for $, $$, $$$ and $$$$.

How do I enable the super-fancy filter slider for pricing?

The page I need help with: [log in to see the link]