To label my boxes, I use vinyl tag holders.
These industrial tags come in
several standard sizes
Sizes I have considered going with:
- #5 — this is the best size to actually fit the space available
- #8 — this is the closest size that would handle standard 3x5" index cards, so I could buy refills at a local store
(see also -- there are some similar products available.
These are even better, because they 1) fit a 3x5 card, albeit a trimmed one, 2) they fit the space perfectly, and 3) they're top-loading, not side-loading.
(for a 4x3" badge)
Vinyl badge holders
3x5 press-on vinyl envelopes
oh my gosh, perfect