cant apply skybox/cubemap to a sphere

I am trying to create a simple photosphere in VR by applying a cubemap to the inverse of a sphere. I create a material and set it to skybox/cubemap. This is the only 'cubemap' shader i can find in the options when selecting shader type. I import my .jpg texture of the 360 panorama i want to map, set its texture type to cubemap and set its mapping to lattitude-longitude. I drag this cubemap texture onto my skybox/cubemap material and it gets assigned. When i try and drag this material onto...

cant apply skybox/cubemap to a sphere