Sediment filter - Dual Gradient Density 25 / 1 micron 20" x 4.5" by CFS Whole House Sediment filter - Dual Gradient Density 25 / 1 micron - 20" x 4.5" 25 micron outer layer, 1 micron inside layer sediment filter. Reduces dirt, sand, silt, and rust particles. 2 separate gradient density layers provide triple the dirt-holding capacity of similar sized filters. Designed for purity with chemical and bacteria resistance Fits Big Blue 20" x 4.5" filter housing, and Home Master Water Filter models #HMF2SdgB1, #HMF2SdgC 25 micron outer layer, 1 micron inside layer sediment filter. Reduces dirt, sand, silt, and rust particles. 2 separate gradient density layers provide triple the dirt-holding capacity of similar sized filters Designed for purity with chemical and bacteria resistance Fits Big Blue 20" x 4.5" filter housing, and Home Master Water Filters