I have no idea, it looks so uncomfy but he seems to love it! Occasionally I've noticed he'll hang his front half over the edge?!What a cutie! Glad you're supporting his bum as piggy bums are quite heavy & could hurt their backs if left dangling. Wonder why he likes to lay like that, silly boy! I have a poochie who likes to lay with her head dangling over the edge of the bed or sofa, can't work out why.