Opel Steering Wheel Puller
It's a bit hard to see in the picture, but those "arms" are just common 5/16 inch grade 5 bolts, with the heads ground down. I happened to use carriage bolts, which gives a rounded pulling lip with an "edge", while a regular bolt will provide a thicker lip. Your choice. I guess the thicker lip would be stronger. Or you could use a grade 8 bolt, but it is tougher to grind to shape.
A picture of Otto's puller can be seen on a later post.
Mine are approximately 4 inches long (but three inches would work), and you grind the bolt head so that it is off-set (lip on one side, none on the other), and "just" fits through the oval hole in the horn button. Slip the arms through the puller beam (available at any auto center) and then rotate each bolt so that the lip points to the inside. Tighten the center bolt against the shaft (with the nut off, of course), and the wheel should pop off. Remember to mark the wheel position relative to the shaft, so it goes back on straight.
DON'T use a hammer to help it off, either by striking the column shaft or the underside of the steering wheel. You risk damaging the "Energy Absorbing, Locking Column", by loosening the plastic injections that maintain steering shaft rigidity. (Just reading from the factory service manual). If you have a factory manual, look at the photo in figure 90-32, page 90-16, to see it in action. They even have marked the bolts to indicate which direction the "lip" is facing. Oh, look at that! I did it to mine too!
HTH