3 in. installation horizontal vent kit required for venting the Bosch AquaStar 2700ES horizontally through-the-wall. Comes assembled as a kit for convenience. Allows the user to vent the 2700ES up from the water heater and straight out the wall. Kit includes: 3 in. adjustable adapter, (2) exhaust/intake vent hoods with 10 in. sleeves, 90 degree elbow, wall thimble