I ordered the medium dog car seat thinking it was the same size as my first dog car seat, but it is about half a size larger than the one I was replacing. Havent travel with my sig in it yet so will have to let you know after this weekend whether my Miniture Schnazer likes it or not. I am concerned with the size of the pillow insert. I believe it is too high in the front and my dog will fall over the front section of the seat due to the higher position of the pillow insert. I think I may try it without using the pillow insert to see if that will be a safer height but the bottom of the unit is not comfy feeling. Rather awkward design. The unit looks great except for the thickness of the pillow. Is there a thinner pillow insert available for mthis unit?