Pharmaceutical Vial Seals by Size: 13 mm to 34 mm

Autofits makes pharmaceutical vial seals in five neck sizes: 13, 20, 28, 32 and 34 mm. The size refers to the vial’s neck finish, not its nominal volume, and it follows the ISO 8362-1 dimensions for glass injection vials. This hub shows which seal designs come in each size, with key inner diameters and heights from the engineering drawings.

There is no 30 mm size in the range; the sizes are 13, 20, 28, 32 and 34 mm. Use the table below to find your neck size, then follow the link to the dedicated page for that size.

Key takeaways

Vial seals are sized by the neck finish, not the vial volume; a “20 mm vial” means a vial with a 20 mm neck finish.
Autofits offers five sizes: 13, 20, 28, 32 and 34 mm. There is no 30 mm size.
The flip-off Optima covers the full span, 13 to 34 mm; other designs cover a subset of sizes.
Neck finishes follow ISO 8362-1, which defines the glass vial dimensions the seal must match.
Match the seal size to the vial neck and the rubber stopper of the same finish, so the crimp seats cleanly.
Per-size pages give the full dimension set; this hub gives inner diameter and total height as a quick reference.

How vial sizing works

A vial’s “size” is the diameter of its neck finish, the flanged opening that the stopper seats into and the seal crimps under. It is quoted in millimetres: 13 mm, 20 mm, 28 mm and so on. This is a packaging dimension, not the same as the vial’s fill volume; a 2 mL and a 10 mL vial can share the same 20 mm neck finish.

Three parts have to agree on the size: the vial neck, the rubber stopper seated in it, and the seal crimped over both. If they match the same finish, the aluminium rolls cleanly under the neck flange and compresses the stopper to form the sterile barrier. The glass vial dimensions themselves are defined by ISO 8362-1; the seal is built to match.

When you specify a seal, start from the neck finish of the vial you are filling, then choose the closure design (flip-off, pull-ring, tear-down or all-aluminium) that suits how the product will be opened.

Sizes and dimensions

The table shows which designs come in each size, with the seal’s inner aluminium diameter (the dimension that seats over the neck) and total seal height. Dimensions are from the Autofits engineering drawings. Values not on the drawings are shown as “on request”; for the complete dimension set at a size, see the per-size page.

Size	Seal designs available	Inner Ø, alu (D1)	Total seal height	Per-size page
13 mm	Optima (flip-off), Tear-Down (alu-plastic), Tear-off (all-alu)	13.36 min (Optima)	7.62–8.38 (Optima)	13 mm seals
20 mm	Optima, Pull-Ring, Tear-Down, Tear-off, Tear-down (all-alu)	20.22 min (Optima)	9.02–9.91 (Optima)	20 mm seals
28 mm	Optima (flip-off)	27.60–28.20	11.06–12.06	28 mm seals
32 mm	Optima, Pull-Ring, Tear-Down, Tear-off	32.10–32.90 (Optima)	14.30–15.50 (Optima)	32 mm seals
34 mm	Optima (flip-off)	33.60–34.00	15.00–16.00	34 mm seals

Notes on the dimensions

Diameters and heights above are for the flip-off Optima except where noted, since it is the design offered across the widest size range. The all-aluminium and pull-ring designs have their own dimensions at each size; see the per-size pages and the family pages.
At 20 mm, the Optima inner alu diameter is 20.22 mm (min) and the outer PP disc reaches 23.14 mm (max), with a total height of 9.02 to 9.91 mm.
At 13 mm, the Optima inner alu diameter is 13.36 mm (min) and total height is 7.62 to 8.38 mm.
At 32 mm, the Optima inner alu diameter is 32.10 to 32.90 mm and total height is 14.30 to 15.50 mm.
Maximum opening forces are 30 N at 13 mm, 35 N at 20 mm, 35 N at 28 mm and 65 N at 32 mm, varying with the number of bridges. No 34 mm opening-force value has been published.

Choosing the right size

If you already know your vial neck finish, match it directly: a 20 mm neck takes a 20 mm seal and a 20 mm stopper. If you are specifying from scratch, the common injectable sizes are 13 mm (small-volume vials) and 20 mm (the most widely used finish), with 28, 32 and 34 mm for larger vials and lyophilisation. Once the size is set, choose the family by opening action:

FlipTop® Optima for flip-off injectables and colour-coding, across 13 to 34 mm.
FlipTop® Pull Ring for full-seal removal, at 20 and 32 mm.
FlipTop® Tear-Down for twist-off, used mainly for oral vaccinations, at 13, 20 and 32 mm.
Tear-off seals for an all-aluminium closure, at 13, 20 and 32 mm.

Quality and standards

Seals at every size are built to the same quality system: ISO 9001:2015, ISO 14001:2015 and ISO 15378:2017, with a Drug Master File (DMF 18100) and CFDA registration (B20200000501). Combination seals follow ISO 8362-6 and all-aluminium seals relate to ISO 8362-3; the glass vial necks they match follow ISO 8362-1.

Aluminium is alloy AA8011 with an epoxy lacquer coating (21 CFR 175.300); PP discs are moulded in-house on Toyo machines. Every seal is 100% camera inspected, with AQL set at critical = nil, major NMT 2.5%, minor NMT 4% (tailorable), and is available Regular, Ready-to-Use (RTU) or Ready-to-Sterilise (RTS). Production is in the 75,000 sq ft Nashik facility with an ISO Class 8 cleanroom. See the quality page and ISO 15378.

Frequently asked questions

What does the size of a vial seal refer to?

The size refers to the vial’s neck finish: the diameter of the flanged opening that the stopper seats into and the seal crimps under. It is quoted in millimetres, such as 13 mm or 20 mm. It is not the vial’s fill volume; vials of different volumes can share the same neck finish.

What vial seal sizes does Autofits make?

Autofits makes seals in 13, 20, 28, 32 and 34 mm. There is no 30 mm size. The flip-off Optima is offered across all five sizes; the pull-ring, tear-down and all-aluminium designs cover a subset, as shown in the table above.

Is there a 30 mm vial seal?

No. The Autofits range is 13, 20, 28, 32 and 34 mm. There is no 30 mm product. If you need an intermediate size, the nearest options are 28 mm and 32 mm.

How do I match a seal to my vial?

Match the seal size to the vial’s neck finish and to the rubber stopper of the same finish. The three parts must share the same size so the aluminium crimps cleanly under the neck flange. The glass vial neck dimensions follow ISO 8362-1.

What is the most common vial seal size?

The 20 mm finish is the most widely used for injectable vials, which is why it is offered across every design in the range (Optima, pull-ring, tear-down and all-aluminium). The 13 mm finish is common for small-volume vials.

Sources

ISO: ISO 8362-1, Injection containers and accessories, Part 1: Injection vials made of glass tubing (https://www.iso.org/)
ISO: ISO 8362-6, Injection containers and accessories, Part 6: Caps made of aluminium-plastics combinations for injection vials (https://www.iso.org/)
Autofits product master spec data (engineering drawings and FlipTop Seals dossier)

*Last updated: 2026-06-26. This page is general technical information, not regulatory or compliance advice; confirm current standard editions and requirements with the issuing bodies.*