we buy the first set because we be potty training and this be the set they have at we toddler 's day care . we buy the second set -lrb- to travel in the car -rrb- because the first set be such a success . we son love it , and start use it strait away with no problem . the seat be not a perfect fit for we toilet seat : the toilet seat be longer , so the thoma seat slide back and forth . however , we solve that with a moist wipe box wedge in behind the thoma seat . we four year old can put it all together on he own , so he can go pee in the middle of the night without we help . he move the step stool easily from the toilet bowl to the sink . the rubber grip on top stop he from slip . the cushion seat -lrb- which be entirely wrap in plastic -rrb- detach easily from its plastic base , so you can wash both part .