44 ml. The colors on the smal comparator that the R-0014 uses are not exactly the same as the ones on the large comparator that R-0004 uses but they are fairly close. You can also order the large comparator for the 2000 series testkits from Taylor as an alternative. It'a about $9-10. There are three of them, one for the FAS-DPD kit (9058), one for the DPD high (9056), and one for the DPD low (9057) but the pH section is the same in all three. The one for the FAS-DPD test costs slightly more than the other two but if you are only interested in measuring pH then any of them are fine.