Frits come in differing standard porosities, and a full range of diameters, from tiny to 380 mm. We can provide frits of all porosities and various diameters, although stock sizes will always be less expensive. We are distributors for ROBU porous glass filters, and stock mostly their frits, so the P- series porosities are easy for us.

Custom and precision dimensions are available as special orders from Germany.

Fritted filter disks are available in a range of diameters. In millimeters, they start at 5, 10, 20, 25, 30, and up in ten mm increments to 380 mm diameter (!). The really big diameters are really expensive (if you have to ask, you probably can't afford them). We stock many of the smaller to medium sizes in the most useful porosities. Custom sizes are available; please contact us with your specifics. The thicknesses of the frits range from 2 - 3 mm for small sizes to 8 - 10 for the larger (~150 mm); they are intended to withstand a pressure differential of one atmosphere (i.e. vacuum).

Below are the porosity specifications for the major manufacturers, and the pore volumes for different porosities.

Each of the three systems of pore size specification generally cover your common needs. There are a few specialized porosities in the finer range, such as 0.5 - .75 µm, in limited thicknesses and diameters.

Porosities of sintered glass filters are determined dynamically: air is forced through a frit just immersed in water until a bubble goes through. The pressure required correlates with the pore size, according to theory: pore diameter (in microns) = 30 * surface tension (in dynes/cm) / pressure (in mm HG). This should correlate with the average pore size of the whole frit.