The JOBO Drum Paper Serie 2840 is the combination of the base 2820 plus the 2870 extension.
The 2820 Test Drum is identical to the 2840 base is identical to the 2820 Test Drum, even they have no label. Lots of people on the web where asking if they can use de the base of the 2840 Drum for 4″x5″ papers. At the answer is yes! Is exactly the same drum with no label in it! You can use it for test strips or for developing 2 sheets max. of 10cm x 12cm papers.
Here is the Drum vs Chemicals vs Paper table:
| Drum | Chemicals (ml) | Papers |
| 2820 | 40 ml | 2x (10cm x 12cm) |
| 2840 (2820+2870) |
120 ml | 4x (13cm x 18cm) |
| 2x (18m x 24cm) | ||
| 2x (20cm x 25cm) | ||
| 1x (24cm x 30cm) | ||
| 1x (28cm x 35cm) | ||
| 1x (30cm x 40cm) |