Our 90 pound husky just had ACL surgery and I bought this so he could get in and out of the SUV.  It is a great ramp, easy to use, very sturdy, a cinch to unfold and very lightweight.  The tread is very good and provides for sure footing.  We have used it outside over a few steps for him and it has been left outside in the rain overnight.  It is plastic, so being outside doesn't hurt it and the water runs right off it.  I am really happy with it.