This is a layerable product, which means that it goes over other clothing.

Unlike non-layerable clothing, layerable clothing does not make your avatar body conform to it, so you have to wear regular clothes under layerable clothing products that shape and size your avatar's body. such as an AP-rated nude suit (clothing made invisible) or skin tight underwear. The underclothing (can be "nude suits" for avatars with AP) bottoms must be for the regular avatar hip size in order for this bathrobe to work over it. But you can wear skintight clothing or an AP nude top in the Muse bust size with this bathrobe. This bathrobe is derived from a non-layerable product and some clipping with the body occurs in some places in some poses and animations, especially in the back and around the arms. So you should try on this product with your under clothing and your avatar poses, etc. to see if it is acceptable to you before you buy it.

You can click on the picture below and go to the non-layerable AP version of this product