The size of the pores in the gel is determined by the total percentage of gel that consists of acrylamide and bisacrylamide monomers (%T) and the percentage of acrylamide that is cross-linker (%C).
Both our stacking gel and our resolving gel use acrylamide with the same percentage of cross-linker (C = 3%) but an increased amount of acrylamide in the resolving gel results in the gel running slower, which better resolves proteins of different sizes. For the stacking gel we use 4% T and for the resolving gel we use 10% T