The ScoopFree Ultra Self-Cleaning Litter Box features everything the original self-cleaning litter box plus 3 additional options, a privacy hood, adjustable rake delay time and health tracker. The ScoopFree Ultra adjustable rake delay allows you to change the delay rake time to 5, 10 or 20 minutes after each use; sensor automatically resets after each time your pet enters the box. The privacy hood holds in the Premium Blue Crystals litter while providing privacy. ScoopFree Ultra's health tracker allows you to monitor the frequency of times your pet uses the box. The plastic lined disposable tray creates a barrier against leakage. Each litter tray should be replaced 20-30 days for one cat, 10-15 days for two cats and 7-10 days for three or more cat households.