The K&H EZ Window Mount Kitty Sills are the easiest, strongest, most versatile window sleeper on the market and are now available in versions from 1 to 4 levels! This awesome product is available in single-level, double stack, triple stack, and quad stack for single or multiple cat households. The K&H EZ Window Mount Kitty Sills provide your cat/cats a front-row view of nature, weather, people and more without taking up valuable floor space. Cats love to bask in the warm sun and thrive on having a high vantage point. As an added bonus this will assist in keeping messy hair off of your furniture! The K&H EZ Window Mount Kitty Sills are like no other on the market. The patented design enables you to quickly fold up your kitty sill WITHOUT removing it from the window, allowing full functionality of your curtains or blinds. This feature is included in all versions; the Single Level, Double Stack, Triple Stack, and Quad Stack styles. Why settle for a Kitty Sill that restricts your blinds or curtains when you don't have to?