iSpring FD15 10-Inch by 2.5-Inch Refillable DI De-Ionization Filter RO/Aquarium Re-fillable DI filter for RO DI system 2.5" x 10" inline filter Fits most RO DI systems, including those brand name models Refill 0 ppm Ion DI(De-Ionized), remove hard water material from the water and create 0-1ppm Great in reducing TDS level in your water