From the manufacturer:
Trailer Aid Plus is the fast, safe and easy way to change a trailer tire on a tandem wheeled trailer. You pull the good tire up onto Trailer Aid Plus to raise the flat tire up 5.5" for changing. Trailer Aid Plus has an additional 1" lift more than the original Trailer Aid and is perfect for RV trailers and horse trailers. It is great for horse trailers so you do not have to remove your horses in order to change a flat tire. The extra 1" lift is handy when performing routine maintenance on the trailer. Lifetime guarantee.
I have not had to use this to change a flat tire (And hopefully I never will) but I keep it with me just in case. I have used it to grease the bearings and it was very easy to use. It’s light weight, made of very strong plastic and stores easily. It seems to be a much more practical option than a jack and gives me piece of mind knowing that I could easily change a tire on the side of the road if necessary.