This kit includes all the parts you'll need to add a second diffuser on to the 1/4 HP Easy Pro/Sentinel aerators. The stock 1/4 HP kit only comes with a single diffuser but due to the good air output of this pump you can actually run two diffusers on it if you wish. This will help distribute the aeration better throughout a pond, particularly if it's shallow, or quite oblong in shape. The kit includes a 2 way valved manifold, 100' of additional weighted 3/8" airline, and the second single plate diffuser, and connectors.