I am used to using 500 mL for ten sheets in an Expert drum, but that is for color only. I process b/w using other methods. This insert for the Patterson tanks really is not all that bad on chemistry. I use at least 250 mL just to process a single sheet in a tray, or 2 whole liters when doing a batch of 8-10 in a deep tank, so it is better than either of these options. The six sheets equal 1.5x80 sq-in, which is not far out of line for that volume of chemistry. While there are better options (such as the SS Nikkor that is as efficient as my Jobo tank), I don't think this is a bad one.