Click to expand Tap to zoom 4-Zone Module for SL1600 by Weathermatic Save $ -62.95 $ 62.95 SKU SLM4 1 2 3 4 5 6 7 8 9 10+ Quantity Quantity Add to cart Expansion module for use in the SL1600 Series of controllers. Module expands the number of usable zones in by 4.