First I don't know how they differ, if they differ, and I think Powerstep have stopped making them. My darling wife has a rare disability where all of her muscles are wasting away and she is unable to get up a normal height step let alone three or a flight. I have come across the above that are very expensive and was hoping one of the members here might have one for sale or know of someone that has one for sale. I envisage it would also be helpful in the garden and possibly in the home. Not wishing to be too morbid I feel that this is a last ditch attempt at being able to continue caravaning/motorhoming. Keeping our fingers crossed.