Two numbers decide whether a label roll fits: the core's inner diameter and the roll's outer diameter. Printers publish limits for both; many label sellers publish only one.
| Printer / holder | Core (ID) | Max roll OD |
|---|---|---|
| Zebra ZD421d | 0.5 in and 1 in standard; 1.5, 2 and 3 in with optional adapters | 5.00 in |
| Zebra ZD220d | 0.5 in and 1 in standard | 5.00 in |
| iDPRT SP410 | Not published | 5 in |
| Arkscan 2054A-LAN | Not published | 5 in (Arkscan notes "outside wound") |
| POLONO PL60 | Not published | 5 in |
| Rollo label holder (external) | 1 in and larger | 6 in |
External-feed printers (Rollo, MUNBYN, Phomemo 241BT) don't hold rolls themselves; the holder sets the limit.
Rollo publishes its 500-label 4x6 roll at 1.5 in core, 5.125 in OD. That fits Rollo's holder (≤ 6 in OD, ≥ 1 in core) but is too large for any 5 in internal roll bay, even with a Zebra core adapter.
Many generic rolls list only the label count and core. You can estimate the OD from the wound material's cross-section:
OD ≈ √( core OD² + (4 ÷ π) × roll length × label-plus-liner thickness )
Assumptions for 4x6 rolls: each label plus gap ≈ 6.125 in of roll length; label + liner ≈ 0.006 in thick (Zebra's ZD421 accepts 0.003–0.0075 in media); a 1 in core tube is about 1.25 in outside, a 1.5 in core about 1.75 in.
| Roll | Estimated OD |
|---|---|
| 250 labels, 1 in core | about 3.6 in |
| 500 labels, 1 in core | about 5.0 in (borderline for a 5 in bay) |
| 500 labels, 1.5 in core | about 5.1 in (Rollo publishes 5.125 in) |
The estimate for the 1.5 in, 500-label roll lands within about 0.03 in of Rollo's published figure, which suggests the assumptions are reasonable. It's still an estimate: thicker stock or tighter winding changes the result. When a roll is near 5 in, choose 250-label rolls or fanfold.
Best for: Printers that load 4x6 rolls inside on a 1 in core, such as Zebra desktop models
250-label 4x6 rolls on a 1 in core with a stated “not compatible with DYMO & Brother” exclusion.
Caveat: BETCKEY does not publish the roll's outer diameter; confirm it is under your printer's limit.
Best for: Rollo or other external-feed printers used with a roll holder
A 500-label 4x6 roll on a 1.5 in core, 5.125 in across—too big for printers with a 5 in internal limit.
Caveat: Needs a roll holder; the 5.125 in diameter won't fit inside Zebra, iDPRT, Arkscan or POLONO printers (5 in max).