I have no idea why people have said the surface is bad or that it isn't strong ... The vinyl surface is formed over the actual structure and though not too smooth ... you don't want it too smooth.  This ramp is extremely sturdy and easily supports my 175# great dane to get in and out of our camper (and fits over the threshold really nicely). It is heavier than the aluminum ones but my dogs don't like those ... they don't seem to trust them.  Put these on the ground and use treats to get your dog to walk back and forth across them for a few days ... they will adapt and get used to them. If you have a short run of stairs in your house ... put them down and you may find your dog having fun walking up and down the stairs.