If it's on the top step, it's usually a low flow. Anywhere else it's usually the high flow. The difference between the two is the low flow has a smaller diameter outflow hole than the high flow.
If you're the original owner of the pool, you have a lifetime warranty on the system and A&A will replace the pop-ups for free. Otherwise, look around for the best price on an original A&A pop-up. They can be had for as low as $45. There are several internet based businesses in the PHX area that have them.