We have a 4yr old Boxer who we transitioned from laying on the couch to the floor with this bed, and it could not have gone more smoothly. She has had other beds in the past but has never taken to one like this. Because she prefers to lay with her head elevated (think pillow :)), the bumpers are perfect, always giving her enough cushion no matter what position she is in. She is 52 lbs and we ordered the medium size and it is perfect - she likes to curl up and feel enclosed, and she still has more than enough room to stretch out. HIGHLY recommend.