Pentair WhisperFlo® 075252 Power End Sub Assembly for WF-3, WF-24 1 per 2 HP Full Rated 3 per 4 HP Up Rated High Performance Pump - The Pentair Energy Efficient Power End Sub Assembly works with the first and only single-speed pump models to use NEMA Premium® Efficient motors for pool applications. Meaning you get balanced flow and greater efficiency in your single-speed, single-phase, Permanent Split Capacitor motor, greatly reducing operating costs.