If you're not going too far, I use a sheet. I folded it in half and whip stitched the two long sides. My Tank isn't all that thrilled about going in it, but after about ten minutes in the car, he's asleep(with something over the sheet, like a coat or a blanket) to make it dark. Tank is four and a half feet long. You can adjust the sheet size accordingly. My Vet is about twenty five miles away, so this works. I even took him on a three hour long trip in it and he was just fine.