Fiji Cube Double 4" Quiet Filter Sock Holder 2nd GenNew Product. Available now. Fiji Cubes 2nd Generation Quiet Filter Sock Holders are easy to install filter bag holders for any sump filtration system. This innovative filter sock holder design allows water to flow through the designed chamber to reduce the noise from the drain. This sock folder features filter sock and filter floss capability. It also has a lid to prevent splashes from the drain which helps to keep your sump surrounded clean and nice.