I have a Step-N-Seat which is the same thing and luv it. Took ten minutes to mount and I mounted it in the center of tailgate. My dogs use it to load, I can use it as a seat and can step up into bed of truck easily.
I bought it online from stepnseat.com for around $165.
I like the Rodon step. It's easy to unfold and is sturdy enough to support up to 250lbs. It locks in place with a spring loaded pin when you unfold it and also locks together when you close it back onto the tailgate.