Size exclusion chromatography (also known as gel filtration) is a chromatography method based on the size and shape of biomolecules. SEC resins have porous structure, which enables longer retention time for smaller biomolecules by letting them enter deep in the beads. Since resins with different pore sizes have different fractionation range, the key for SEC resin selection lies in the right fractionation range, in addition, factors including mechanical property and easy scale-up should also be taken into account.