Sleepytroll Bed Rocker Feet will help to transform your baby's crib into a rocking cradle in just a few minutes. Combined with the Sleepytroll Smart Baby Rocker and crib adapter, parents don't have to rock the crib themselves, these devices do it all. The foot kit includes 4 screws. Sleepytroll rocker feet can only be installed on wooden baby cots. Developed in Norway. Patented worldwide.