Vial Size Chart: ISO Vial Sizes and the Seal That Fits Each
Glass injection vials made from tubing are sized under ISO 8362-1 from 2R to 100R, and the vial’s neck, not its capacity, sets the seal: 2R and 4R vials have a 13 mm neck and take a 13 mm seal, and 6R to 100R vials have a 20 mm neck and take a 20 mm seal. Autofits makes crimped vial seals in 13, 20, 28, 32 and 34 mm; the 28, 32 and 34 mm seals fit larger-neck vials such as moulded-glass vials under ISO 8362-4. The tables below match each ISO vial size to its seal, then give the drawing dimensions of every Autofits seal.
ISO 8362-1 vial sizes and the seal for each
| ISO vial size | Neck finish | Seal size | Autofits seals that fit |
|---|---|---|---|
| 2R | 13 mm | 13 mm | FlipTop Optima 13 mm, FlipTop Tear-Down 13 mm, Tear-off 13 mm |
| 4R | 13 mm | 13 mm | FlipTop Optima 13 mm, FlipTop Tear-Down 13 mm, Tear-off 13 mm |
| 6R | 20 mm | 20 mm | FlipTop Optima 20 mm, FlipTop Pull Ring 20 mm, FlipTop Tear-Down 20 mm, Tear-off 20 mm, Tear-down 20 mm |
| 8R | 20 mm | 20 mm | All 20 mm seals above |
| 10R | 20 mm | 20 mm | All 20 mm seals above |
| 15R | 20 mm | 20 mm | All 20 mm seals above |
| 20R | 20 mm | 20 mm | All 20 mm seals above |
| 25R | 20 mm | 20 mm | All 20 mm seals above |
| 30R | 20 mm | 20 mm | All 20 mm seals above |
| 50R | 20 mm | 20 mm | All 20 mm seals above |
| 100R | 20 mm | 20 mm | All 20 mm seals above |
| Larger-neck and moulded vials | 28, 32 or 34 mm | Same as the neck | FlipTop Optima 28 mm, 32 mm, 34 mm, FlipTop Pull Ring 32 mm, FlipTop Tear-Down 32 mm, Tear-off 32 mm |
The number in an ISO size is a guide to capacity, but vials of very different capacity share one neck, which is why a 6R and a 50R vial take the same 20 mm seal. Always confirm the neck from the vial maker’s drawing; the vial standards are explained on ISO 8362-1 and vial neck types.
Key takeaways
- Five seal sizes: 13, 20, 28, 32 and 34 mm. The size is the neck finish, not the vial capacity.
- D1 is the inside diameter of the aluminium skirt. On a 20 mm FlipTop Optima it is 20.22 mm minimum, just over the neck it fits.
- Aluminium thickness runs from 0.16 to 0.20 mm on 13 and 20 mm Optima seals up to 0.21 to 0.25 mm on the 32 mm.
- Bridge count varies by size: 6 on 13 and 20 mm Optima, 8 on 28 and 34 mm, 12 on 32 mm.
- Maximum opening force is 30 N at 13 mm, 35 N at 20 and 28 mm, and 65 N at 32 mm.
- Glass vial necks follow ISO 8362-1 (tubing) and ISO 8362-4 (moulded); aluminium-plastic caps follow ISO 8362-6 and all-aluminium caps ISO 8362-3.
- ISO 8362-1 vials: 2R and 4R take a 13 mm seal; 6R to 100R take a 20 mm seal.
- Pilfer-proof (ROPP) caps are a separate family sized to bottle necks: 22, 25, 28, 35 and 38 mm.
How to read seal size against vial neck
Match the seal to the neck finish on the vial drawing, then check that the skirt height covers the stopper flange and the neck bead together. The seal diameter is fixed by the neck. The height has to suit the stack it crimps over: the flange of the rubber stopper sitting on top of the glass bead. A seal that is too short leaves too little skirt to roll under the bead; one that is too tall leaves loose aluminium after crimping.
| Seal size | Neck it closes | Typical container | Autofits lines in this size | Cap standard |
|---|---|---|---|---|
| 13 mm | 13 mm neck finish | Small tubular glass injection and lyophilisation vials | FlipTop Optima, FlipTop Tear-Down, Tear-off | ISO 8362-6 (alu-plastic), ISO 8362-3 (all-aluminium) |
| 20 mm | 20 mm neck finish | The most common injection vial neck, tubular or moulded | FlipTop Optima, FlipTop Pull Ring, FlipTop Tear-Down, Tear-off, Tear-down | ISO 8362-6, ISO 8362-3 |
| 28 mm | 28 mm neck finish | Larger-neck injectable and lyophilised vials | FlipTop Optima | ISO 8362-6 |
| 32 mm | 32 mm neck finish | Large-neck vials for high fill or reconstitution | FlipTop Optima, FlipTop Pull Ring, FlipTop Tear-Down, Tear-off | ISO 8362-6, ISO 8362-3 |
| 34 mm | 34 mm neck finish | The largest necks in the range | FlipTop Optima | ISO 8362-6 |
Container types are typical practice, not a limit. Two vials of very different capacity often share one neck, which is why a 2 ml and a 10 ml vial can take the same 20 mm seal. The broader decision is explained in how to choose a vial cap size, and the seals are grouped by size on the vial seals by size pages.
FlipTop Optima dimensions (aluminium-plastic flip-off)
The FlipTop Optima is the only line made in all five sizes, so its table doubles as the reference chart for the range. All values in mm.
| Size | D1, inner aluminium | D2, outer disc | Disc height | Inner aluminium height | Total seal height | Aluminium thickness | Bridges |
|---|---|---|---|---|---|---|---|
| 13 mm | 13.36 min | 14.99 max | 2.90 to 3.30 | 6.15 to 6.40 | 7.62 to 8.38 | 0.16 to 0.20 | 6 taper |
| 20 mm | 20.22 min | 23.14 max | 3.20 to 3.60 | 7.37 to 7.62 | 9.02 to 9.91 | 0.16 to 0.20 | 6 taper |
| 28 mm | 27.60 to 28.20 | 30.10 to 31.10 | On request | 8.70 to 9.30 | 11.06 to 12.06 | 0.17 to 0.23 | 8 |
| 32 mm | 32.10 to 32.90 | 35.50 to 36.50 | On request | On request | 14.30 to 15.50 | 0.21 to 0.25 | 12 taper |
| 34 mm | 33.60 to 34.00 | 35.50 to 36.50 | On request | On request | 15.00 to 16.00 | 0.20 to 0.25 | 8 taper |
FlipTop Pull Ring and FlipTop Tear-Down dimensions
Both lines remove the whole seal after opening; at 20 mm the Pull Ring is drawn from thicker aluminium than the Optima, 0.18 to 0.22 mm against 0.16 to 0.20 mm. All values in mm.
| Line and size | D1, inner aluminium | D2, disc | Disc height | Inner aluminium height | Total or assembled height | Aluminium thickness | Bridges or fins |
|---|---|---|---|---|---|---|---|
| Pull Ring 20 mm | 20.00 to 20.60 | 22.00 to 23.00 | 3.00 to 4.00 | 7.00 to 7.60 | 9.00 to 10.00 | 0.18 to 0.22 | 6 taper bridges |
| Pull Ring 32 mm (flower) | 32.15 to 32.40 | 36.20 to 36.60 | On request | 13.20 to 13.60 | 14.30 to 15.30 | 0.20 to 0.26 | 8 fins |
| Tear-Down 13 mm | 13.30 to 13.50 | 14.80 to 15.40 | 3.70 to 4.10 | 6.00 to 6.40 | 6.80 to 8.30 | 0.18 to 0.22 | Bridge design |
| Tear-Down 20 mm | 20.00 to 20.60 | 22.00 to 23.00 | 3.00 to 4.00 | 7.20 to 7.80 | 8.80 to 9.80 | On request | Bridge design |
| Tear-Down 32 mm (flower) | 32.40 to 33.15 | 35.70 to 36.70 | On request | 13.20 to 13.60 | 14.30 to 15.30 | 0.20 to 0.26 | 8 fins |
All-aluminium tear-off and tear-down dimensions
All-aluminium seals have no plastic disc, so D2 is the diameter of the perforated centre that tears away rather than a disc. All values in mm.
| Line and size | D1, inner aluminium | D2, perforation | Total height | Aluminium thickness | Bridges |
|---|---|---|---|---|---|
| Tear-off 13 mm | 13.20 to 13.60 | On request | 6.90 to 7.70 | On request | 2 |
| Tear-off 20 mm | 20.00 to 20.60 | 9.70 to 10.50 | 7.40 to 8.00 | 0.16 to 0.20 | 2 |
| Tear-off 32 mm | 32.40 to 32.60 | 17.80 to 18.20 | 13.00 to 13.60 | On request | On request |
| Tear-down 20 mm | 20.50 to 20.70 | 12.90 to 13.20 | 7.50 to 8.50 | 0.18 to 0.22 | 2 taper |
Opening force by size
Opening force depends on seal size and on the number of bridges that have to break. The figures below are maximums from the FlipTop seals dossier.
| Seal size | Maximum opening force |
|---|---|
| 13 mm | 30 N |
| 20 mm | 35 N |
| 28 mm | 35 N |
| 32 mm | 65 N |
| 34 mm | On request |
Pilfer-proof (ROPP) cap sizes
ROPP caps close threaded bottles, not stoppered vials, so their sizes follow the bottle’s screw-neck finish: 22, 25, 28, 35 and 38 mm. The cap drawing for a specific bottle is confirmed with the quotation. The caps and their liners are on the pilfer-proof caps page.
How to use this guide
Start from the vial drawing, pick the size from the neck, then check three numbers against the vial and stopper: D1, total height and aluminium thickness.
- Read the neck outside diameter and bead height from the vial supplier’s drawing. Tubular glass vials are dimensioned under ISO 8362-1 and moulded glass vials under ISO 8362-4.
- Add the stopper flange thickness from the stopper drawing. The seal’s inner height has to cover the flange and the bead with enough skirt left to roll under.
- Choose the line from how the vial is opened: flip-off, pull ring, tear-down or tear-off. The dimensional rules for aluminium-plastic caps are in ISO 8362-6; for all-aluminium caps, ISO 8362-3.
- Check the crimp on your own capper with production vials and stoppers before fixing the specification. Dimensions confirm fit on paper; a capping trial confirms it on the line.
Piece weight is not a catalogue value. It varies with the design, the disc and the aluminium thickness, and is confirmed with the quotation for the part you order. The full specification for each line, including materials and shelf life, is on the technical datasheets page.
What to send with a sizing enquiry
Send the drawings, not a description, and the matching seal drawing comes back with the quotation.
- Vial drawing, or the vial supplier and part number, with neck diameter and bead height
- Stopper drawing, with flange diameter and thickness
- Seal line and design you have in mind, if any
- Capping machine type and speed
- Whether you need samples for a capping trial
Contact Autofits with the above and the engineering team will confirm the seal size and drawing.
Frequently asked questions
What seal size fits a 10R or 20R vial?
A 20 mm seal. Every ISO 8362-1 tubular vial from 6R to 100R has a 20 mm neck, so 10R and 20R vials both take a 20 mm seal. The 2R and 4R sizes have a 13 mm neck and take a 13 mm seal.
Are 5 ml, 10 ml and 30 ml vial caps the same size?
Often, yes. A vial seal is sized by the neck finish, not by the vial’s capacity, and vials of quite different volumes are commonly made with the same 20 mm neck. A 5 ml vial could also have a 13 mm neck. Read the neck diameter from the vial drawing rather than choosing the seal from the fill volume.
How do I measure a vial neck to choose a seal?
Measure the outside diameter of the neck bead, the rolled lip at the top of the vial, with a caliper, and compare it with the nominal sizes of 13, 20, 28, 32 and 34 mm. Then take the bead height and the stopper flange thickness, because together they set how tall the seal skirt must be. The vial drawing is more reliable than a measured sample.
What is the difference between D1 and D2 on a seal drawing?
D1 is the inside diameter of the aluminium skirt, the dimension that has to clear the vial neck and stopper. D2 is the outside diameter of the plastic disc on an aluminium-plastic seal, or the diameter of the perforated centre on an all-aluminium tear-off or tear-down seal.
How much does a 20 mm flip-off seal weigh?
Piece weight is not published as a fixed figure because it depends on the design, the disc and the aluminium thickness, which on a 20 mm FlipTop Optima runs from 0.16 to 0.20 mm. The weight for the exact part you order is confirmed with the quotation. A standard box holds 6,000 20 mm FlipTop seals.
Which standard sets vial seal dimensions?
ISO 8362-6 covers caps made of aluminium-plastics combinations for injection vials, which includes flip-off seals, and ISO 8362-3 covers all-aluminium caps. Both are written to fit the glass vials of ISO 8362-1 and ISO 8362-4. Autofits aluminium-plastic seals follow ISO 8362-6, and its all-aluminium seals relate to ISO 8362-3.
Related reading
- Vial seals by size, 13 mm to 34 mm
- How to choose a vial cap size
- Technical datasheets for every seal line
- ISO 8362-6: aluminium-plastic caps
- ISO 8362-1: tubular glass injection vials
Sources
- Autofits engineering drawings and FlipTop Seals dossier
- ISO: ISO 8362-1:2018, Injection containers and accessories, Part 1: Injection vials made of glass tubing (https://www.iso.org/standard/74398.html)
- ISO: ISO 8362-3:2001, Injection containers and accessories, Part 3: Aluminium caps for injection vials (https://www.iso.org/standard/33804.html)
- ISO: ISO 8362-4:2011, Injection containers and accessories, Part 4: Injection vials made of moulded glass (https://www.iso.org/standard/57745.html)
- ISO: ISO 8362-6:2010, Injection containers and accessories, Part 6: Caps made of aluminium-plastics combinations for injection vials (https://www.iso.org/standard/52806.html)
*Last updated: 2026-11-06. Dimensions are transcribed from Autofits engineering drawings; the controlled drawing for the part you order is confirmed with the quotation. This page is technical product information, not regulatory advice.*
