The World’s Slowest Drip System Place your F&DS on the top of a six-inch Rockwool cube, and use it along with a variety of interchangeable products such as the World’s Slowest Drippers, aka the Gravity Drippers, as well as the Quicker Drippers, and Eliminators. Eliminates algae and pesticides by covering the media. Measures up to 32 oz (1000 ml) of water. Instantly transforms from a top feed to a top-feeding drip system with the 1/4” nozzle cap. Translucent rubber over-mold on top for viewing water with measurements. Opaque bottom to block light. Four four-way stakes on the bottom for extra stability. Seven raised air slots. Snap and pop technology. Stackable. Reusable. BPA and lead-free rubber and plastic.