..That is an aftermarket seat made by seat concepts, it is a little wider and slightly thicker but the foam is different from the stock seat too. It has really made a difference...
Long rides on a stock XT225 seat can leave a 'Monkey Butt' impression that's not soon forgotten. Anything to make riding it more comfortable is a huge improvement. Wider softer seats like Seat Concepts makes are one of the better choices.
Walmart sells an ATV seat cover as show here that fits the stock XT seat and makes it a lot more comfortable.
Some have rebuilt their stock XT seat with wider foam and re-covered it themselves. Whatever it takes it's a worthwhile project..