A penny sleeve is about two thousandths of an inch of polypropylene film with the card resting directly against it. The adhesive on a permanent vinyl Serial Seal™ is stronger than that film. So for a card with real value: do not seal the sleeve. Sleeve the card, drop it into a top loader, and seal the loader.
That choice changes where the seal lands and nothing else. It is the same 0.75" x 1.77" seal either way, and the only things you pick are the prefix, the starting number and the quantity — three fields on the builder.
The sleeve, by the numbers
A standard penny sleeve is 2-5/8" x 3-5/8" (2.625" x 3.625"; 66.7 x 92.1 mm) and holds a 2.5" x 3.5" card. Ultra Pro lists its sleeve at 2-5/8" wide for cards up to 35pt; some brands market a near-identical sleeve as 2-9/16". Measure the pack in front of you.
It is open on one short edge — the 2.625" top. The other three are factory welds.
Each wall is roughly 2 mil (0.002"), so the open edge is about 0.004" of film plus the card — effectively a zero-thickness edge for seal arithmetic.
Where the Serial Seal™ goes
If you are sealing the sleeve itself, use a FOLD over the open 2.625" top edge. The other three edges carry raised factory welds that tent the film, so the mouth is the only edge a fold sits flat on — and folded there it squares the sleeve up and keeps the face clean for the card. A SINGLE seal lying flat on a face works when you would rather wrap nothing.
The seal is 0.75" x 1.77". Across a 2.625" edge the 0.75" width covers 28.6%, and centered it sits 0.94" clear of each side weld.
Per-face landing is (1.77 - T) / 2, where T is the thickness of the edge you wrap. On a penny sleeve T is about 0.004", so each face gets 0.883" — 24.4% of the 3.625" height. A sleeve is the thinnest thing you will ever fold this seal over, so it is also the most landing you will ever get out of it.
| Style | Where it goes | Per-face landing | Use it when |
|---|---|---|---|
| Fold | Over the open 2.625" top edge | 0.883" | You are sealing the sleeve itself, bulk card inside |
| Single | Flat on one 2.625" x 3.625" face | 0.75" x 1.77", one face | You only want a number on the unit |
| Fold on the top loader instead | Over the loader's 3" top edge, offset about 0.6" from center | 0.854" at 1/16" depth | Any card you would be annoyed to scuff |
Both landing figures above are that formula at T = 0.004" and T = 0.0625". Run it for whatever you are holding.
Measure your own pack rather than trusting a row: a 2-9/16" sleeve puts the weld clearance at 0.91" and leaves the landing alone. The seal is identical either way, which is why the builder never asks what you are sealing — only how many you want numbered.
Why the top loader is usually the right target
Three problems, each enough on its own.
The adhesive sits against the card. A 0.883" patch of vinyl on 2 mil film presses on the card surface underneath for as long as the sleeve stays sealed.
The card cannot come out. Once the mouth is sealed, getting the card out means destroying the sleeve or flexing the card past a stuck edge, and flexing is how corners get dinged.
Taking the seal off takes the sleeve with it. The film gives before the adhesive does, so torn sleeve drags across the card face.
So for anything with value: sleeve the card, load it, seal the loader. The loader takes the seal instead of the sleeve, so nothing adhesive ever sits against the card. Placement figures are in how to seal a top loader.
Never put a seal on a card itself, and think twice about sealed wax or anything whose value depends on an unmarked surface. Seal the holder, the bag, the box or the package.
When a sleeve-only Serial Seal™ makes sense
Bulk. Sorted commons, base lots, set runs, anything you sell by the stack — the sleeve is disposable, and what you want is a number attached to a unit you shipped. A fold over the mouth does that.
The line is simple: if you would care about a scuff on the card, it goes into a top loader. If not, the sleeve is fine.
For lots and stacks, one seal across the container's closure usually beats sealing every sleeve inside it — see how to seal a break stack.
Step by step
- Decide whether this card belongs in a top loader. If it does, stop here: sleeve it, load it, seal the loader.
- Seat the card fully so its top edge sits below the sleeve's mouth, and push the air out toward the opening.
- Photograph the card front and back before sealing, then once more afterwards with the serial legible.
- Lay the sleeve flat with the open edge overhanging a table edge by an inch, so the fold has room.
- Peel the seal and set it on the front face first, top edge aligned to the mouth, centered for 0.94" of clearance to each weld. Roll the remaining 0.883" over the edge onto the back face without stretching it.
- Burnish from the fold outward so no air is trapped in the crease, then give it 30 minutes before shipping. Permanent adhesive builds grip over time.
- Write the serial against the order before the parcel goes out. Once it ships, that row is the only copy you have.
How many do you need
Count the units that leave the building, not the cards. A single you sleeve and load takes one seal, and it goes on the loader. A sorted lot takes one seal across the bag or box closure however many sleeves are stacked inside it — seal every sleeve in a 500-card lot and that is 500 seals for one shipment, where the closure is one.
So the sum is the singles you loader up in a month, plus the lots you ship in a month. Multiply by the months you want covered, then round up to the next twelve: seals come in packs of twelve, with 60 the smallest order.
60 Serial Seal™ minimum · From $30.00 · As low as $0.30 each in bulk.
Run it on your own figures. Say it lands at 35 a month. A quarter is 105, rounding to 108 at the 50c list rate — $54.00. The 120 rung is the same $54.00 at 45c each, so the spare dozen costs you nothing. A year is 420 — $189.00, still 45c a seal — with 600 at $240.00 (40c each) as the next step down a rate card that keeps falling to 30c at 4,200. And if you have never folded one of these over a sleeve mouth, the 60-seal minimum is $30.00 — 50c a seal, enough to try the fold and the single on your own stock before you commit to a year of either.
The rate moves on its own at checkout. There is no code to type, and one tier applies to an order. No setup, die, or design fees, and a commercial license and copyright come with the run. Put the quantity into the builder and the price follows it as you type.
What this does and does not do
On a sleeve the seal bridges film a buyer opens with a thumbnail. What it does is record which unit left you. It says nothing about the card behind the film — not that the card is real, not that it is the one in your listing photo.
A seal can also be taken off a sleeve and a different one put on; on 2 mil film that swap costs someone a cent for a fresh sleeve. None of the material behaviour above changes what this product is. The seal carries a number, and the number is only worth anything because you photographed it and wrote it down. You set the prefix and the start, we print the run in sequence, and no two seals in your order share a number. The record is the asset.
Some layouts print VOID IF DAMAGED. On a sleeve that is a notice about the condition you sold under, not a mechanism — the film gets damaged by whoever opens it, which is what a sleeve is for.
Marketplaces and grading companies run their own processes and publish their own current rules; read theirs. If return disputes are why you are here, the return-fraud page covers how sellers use the numbering.
Common mistakes
- Sealing a sleeve that holds a card you care about. The sleeve is not the protector. The top loader is.
- Folding over a welded edge. Three of the four edges carry a raised weld line, and film over a weld tents and lifts. The mouth is the only edge a fold sits flat on.
- Drifting off-center into a weld. Centered leaves 0.94" of margin per side. On the raised weld line the seal tents and lifts.
- Sealing before photographing. Once it is sealed and in a mailer, the shot you needed is gone.
- Treating the sleeve as your shipping seal. A sleeve travels inside a mailer, and numbering the outer package is a separate job — see how to seal a shipping package.
Questions people ask
Will a Serial Seal™ damage a card in a penny sleeve?
The seal never touches the card, but the sleeve does, and adhesive on 2 mil film puts pressure straight onto the card surface underneath. Put anything with value into a top loader and seal that instead.
Can you take a Serial Seal™ off a penny sleeve?
Not cleanly. The adhesive is stronger than the film it is stuck to, so what comes away is sleeve, not seal. Budget for a replacement sleeve rather than a clean peel. That is a property of the stock and nothing more — a fresh sleeve and a different seal is an option open to anyone.
What size Serial Seal™ fits a penny sleeve?
One size. The seal is 0.75" x 1.77", folded over the 2.625" mouth for 0.883" of landing on each face. The same seal covers every top loader thickness up to 360pt.
Should I seal every sleeve in a bulk lot, or just the bag?
Count it. One seal per sleeve, times the number of sleeves, against one seal across the bag or box closure. If the buyer receives the lot as a single unit, the closure is the thing worth numbering.
What this guide settles is a target, not an order. A sleeve is packaging, not protection — on any card you would mind scuffing, the number belongs on the loader around it, and how to seal a top loader carries the figures and ordering detail. Seal the sleeve only when it is the whole product.
Serial Seal is an independent printer. We are not affiliated with, endorsed by or sponsored by PSA, Beckett, CGC, SGC, Ultra Pro, BCW, eBay, Whatnot, TCGplayer or any card manufacturer. Brand names are used only to describe the products they make. Nothing here is legal advice.