The NIIMBOT B31 takes label rolls from 20mm to 75mm wide. The NIIMBOT B4 takes 20mm to 110mm, which is why it is the only one of the two that prints 100×150mm (4×6") shipping labels. Everything 75mm and under fits both printers, so if you own both, most of your label stock is interchangeable. Lengths run from 8mm to 350mm on both.
Sizes that fit both the B31 and the B4
This is the shared range, and it is where most everyday labelling sits:
- Small rectangles: 25×15, 30×15, 30×20, 30×30, 30×40, 40×15, 40×20, 40×30, 40×40mm
- Medium: 45×15, 50×15, 50×20, 50×30, 50×50, 50×70, 50×80, 40×60, 40×80mm
- Wide (B31's sweet spot): 60×40, 60×80, 70×40, 70×80, 70×100, 75×40mm
- Round: 20mm, 30mm, 50mm and 51mm diameter
- Long strips and multi-lane rolls: 30×170, 40×100, 50×100, 50×170mm, plus 2-lane and 4-lane rolls like 8×170/4L and 15×170/2L for cable and index work
The white sticker range for B31 and B4 covers nearly all of these in one product, and the wider 60–75mm sizes live in the B31 label collection.
Sizes only the B4 can take
Anything over 75mm wide needs the B4:
- 100×150mm — the standard 4×6" courier label
- 100×100mm and 100×60mm — smaller parcel and carton labels
- 100×70mm self-adhesive and 90×50mm shelf labels
- 80×50mm transparent
These all come from the B4 wide-format roll range (50–110mm), which is the one to buy if you are printing airway bills or warehouse and fulfilment labels. Note that this roll range is not listed in the B31 collection, because the B31 simply cannot feed it.
It is not just white paper
Both printers take the same variety of materials, as long as the width fits:
- Transparent labels — for jars, bottles and anywhere you want the surface to show through
- Pure colour rolls in yellow, red, blue, green, orange, pink and brown — useful for colour-coding stock or cafe price tags
- Cable tags in single and double row, five colours
- Freezer labels with adhesive that holds at low temperature
- Matte writable stock, round stickers, price tags, bookmarks and cartoon designs
How to check what you have loaded
Genuine NIIMBOT rolls carry an RFID chip, so the printer reads the label size the moment you close the lid and the app configures itself. If you are unsure what is in the machine, open the NIIMBOT app while connected and it will tell you. This is also why unbranded rolls cause trouble — no chip means no auto-detection, and you have to set the size by hand.
What will not fit
The B31 will not take anything wider than 75mm, so 4×6" shipping labels are out — no setting changes that. Neither printer takes thermal transfer stock: the PET labels and ribbons used by the N1 and M2 are a different technology and will not print on a direct thermal machine.
Buying the right roll
Work backwards from the job. Parcels mean 100×150mm and therefore the B4. Product tags, shelf edges and bakery labels sit comfortably in 40–75mm on either printer. Small barcodes and cable tags are fine anywhere from 20mm up.
If you are still choosing between the two machines, our B31 vs B4 comparison covers the decision in full. And if a roll is loaded but printing nothing, that is almost always an orientation problem — see printing blank labels? how to fix it. Every roll ships from our Singapore warehouse.