A part of the column content that separates column packing compartments. In radial columns the packing is supported between two cylindrical frits and the gap between represents the bed height or column length. The outer frit is the column inlet and consequently the sample initially has a large area of stationary phase with which to interact. Frits are porous metal products to prevent unwanted particles from entering the chromatography system. These particles may come from the sample, the solvent or debris generated by the chromatography system itself. Such particles entering the system may lead to clogging of capillaries, interference with the chromatography by changing chromatographic parameters or disturbance of the detector function. Characteristics of a frit, besides the diameter and the thickness, is the porosity (pore distribution, density).