681 Blend Center is a 1 to 4 product system with a stainless steel cover and dedicated fill ports for individual products that limits the selection choice the user makes and provides a large product identification area. Mix and match 1gpm (4 liters / min.) and 4 gpm (15 liters / min.) and choose from blue, red, green, yellow, black, or white buttons. Models include either Action Gap or Air Gap backflow protection.