Weathermatic 4-Zone Module for Pl1600 and Sl1600<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>2 zone hot swappable module</li><li>Fits weathermatic smartline 800 controller</li><li>This module adds four zones at a time to a weathermatic smartline Sl1600 and proline Pl1600</li></ul></div><img src="http://ecx.images-amazon.com/images/I/4143YoQpD8L.jpg" noproxy>