It contains alpha one and alpha two, as shown in the following diagram. But it doesn't contain beta one and beta two. Instead, it contains a slightly different two subunits gamma one and gamma two. And when these four subunits create the tetrimer fetal hemoglobin, notice we no longer have that space inside the hemoglobin that can accommodate the two three BPG. And so, unlike the Dull hemoglobin, the fetal hemoglobin in the presence of two three BPG does not actually bind to two three BPG. And what that means is if we compare the affinity of these two hemoglobin molecules in the presence of the same concentration of two three BPG, we see that because the fetal hemoglobin doesn't actually bind the two, three BPG, that means its affinity for oxygen will be much higher than the affinity for oxygen of adult hemoglobin.