Randy,
That was a generic photo I grabbed off the internet. They come in all sizes and can be found in most building centers. I used a very short version of that sleeve anchor. It was not longer than 3/4 inch long. The machine screw that is comes in these anchors are a very small diameter so I would suggest using a large enough washer to prevent the head of the machine screw going through the hook your attempting to anchor to the wall. The reason I like these is that they pull tightly to the back side of the thin paneled wall material and make a very secure mount. I've used these to hold a towel bar to the back side of our bathroom door as well as to secure a toilet paper holder to the wall of the bathroom (an outside wall at that). Keep in mind the space between the walls when you purchase. Longer doesn't make it stronger, the strength is in how it clamps itself to the wall material.