Irritrol's PC-12-ADD-INT 12-Station Extension Kit (Indoor) comes from the PC Control Series. This is a kit adds a 12-station capacity to your existing indoor PC Control Series controller system. Irritrol has made their name as a brand by selling and marketing exclusively to the professional installer, as a result their products are geared to be dependable and durable. Irrirtrol is now making their products available to you through our website. If you are looking for a product line that will last year in and year out, Irritrol is the brand for you.