State of the art filter media for use in fresh and salt water wet/dry systems.They may be connected together or randomly placed in the filter box. Bio-Pin Balls help produce turbulence, aiding in the gas-exchange process. The suggested usage is 1 gallon of Bio-Pin Balls per 20 gallons for salt water or 35 gallons freshwater. Size Large. Each Bio-Pin Ball has 150 Bio-pins(drip points). There are 74 Balls per gallon, one cu ft. of media has approximately 150 sq ft of surface area.