Pro Clear Aquatic Systems Freedom 4-in-1 Sumps were skillfully designed to provide aquarists with a quiet, sturdy, easy to maintain saltwater filtration system, with features you simply will not find on your average sump. The Freedom 4-in-1 offers 4 filtration methods for saltwater ecosystems; mechanical filtration with 200 Micron filter bags, liquid waste removal with a dedicated protein skimmer chamber (protein skimmer not included), chemical filtration when utilizing the optional Chemical Media Cartridge(s), and biological filtration via built in refugium compartment. Bubble diffuser tubes help silence and remove bubbles as water enters the sump, Eurobracing around the rim of the sump prevents bowing, and includes notches for holding wires, dosing tubes, and keeps return pump tubing snugly in place. The 4-in-1 sumps also include a built in probe holder, making the setup and monitoring of probes sleek and simple, and an adjustable flow gate to customize flow through the refugium section of the sump. Refugium can also be converted to a wet/dry trickle filter with the addition of egg-crate and bio-balls for freshwater use! All Freedom Sumps are made in the USA and include lifetime warranty against leaks and defects due to workmanship. The 4-in-1 Sump 100 features a max flow of 400 gallons per hour, with 1 input, 2 filter socks and 1 media container slot, measuring 16" x 16" x 16" (cube).