TSKgel ODS-120A columns use a 150 Å pore size silica base support. The silica's exclusion limit of 10,000 Da makes them a good choice for the reversed phase chromatography of peptides, small proteins, and environmental samples such as poly-aromatic hydrocarbons.
The "A" signifies that the material is not endcapped. For charged samples, the endcapped TSKgel ODS-120T column is a more suitable alternative.
Bonded phase pore size is indicated by the number in the product description, in this case TSKgel ODS-120A has 120 Å nominal pore size.