Power Steering Cap
Be careful useing that oil cap the original cap is vented.
The pump I got to use as a trade in core and for its cap had an o-ring installed under it as the owner had it on a dirt track car. Well the o-ring twisted into just the right place one day and it will cause presure to build in the pump and blow the reservoir seal.
Ask me how I know. Good thing Napa had a full warrenty and got me a new pump rather then me messing with it.