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Combi Seals

A combi seal is a two-part vial closure: a deep-drawn aluminium shell that crimps under the vial neck flange, with a moulded polypropylene top riveted or seated on it. ISO 8362-6 is the standard for these closures and titles them caps made of aluminium-plastics combinations, which is where “combination cap” and the shop-floor short form “combi seal” come from. Autofits makes combi seals in 13, 20, 28, 32 and 34 mm across three designs: FlipTop® Optima flip-off, Pull Ring and Tear-Down.

This page covers what a combi seal is, why the two materials are combined, how ISO 8362-6 and ISO 8362-7 divide the family, the Autofits range with dimensions, and forms of supply.

Key takeaways

  • A combi seal is an aluminium-plastics combination cap: aluminium does the crimp and the barrier, polypropylene does the user interface.
  • The family standard is ISO 8362-6, caps made of aluminium-plastics combinations for injection vials; ISO 8362-7 covers the variant without an overlapping plastics part.
  • Autofits builds combi seals as Optima flip-off (13 to 34 mm), Pull Ring (20 and 32 mm) and Tear-Down (13, 20 and 32 mm).
  • Aluminium is AA8011 at 0.16 to 0.26 mm depending on size; the plastic top is polypropylene moulded in-house on Japanese Toyo machines.
  • Maximum opening force is 30 N at 13 mm, 35 N at 20 and 28 mm, 65 N at 32 mm, varying with the number of bridges.
  • Finishes are glossy, matte, embossed or printed, in a wide range of colours customised to requirement.

What is a combi seal?

A combi seal is a vial closure built from two materials working on different jobs: an aluminium shell crimped over the rubber stopper to hold the sterile barrier, and a moulded plastic top that gives the user a clean, controlled way to open the vial. The alternative is an all-aluminium seal, which does the crimp but has no plastic component and is opened by tearing the metal.

The aluminium half is the structural part: deep-drawn, lacquered, then rolled under the vial neck flange during capping so the stopper stays compressed against the glass for the shelf life of the product. That job does not change between a combi seal and an all-aluminium seal.

The plastic half is the interface. Polypropylene can be moulded to a shape and a break point that aluminium cannot hold, which is what makes a flip button, a pull ring or a twist-off disc possible, and it takes pigment and print far better than lacquered metal. The trade-off between the two constructions is set out in aluminium-plastic seal versus aluminium seal.

Why the two materials are combined

The combination exists because the crimp and the opening action have incompatible material requirements, and splitting them into two parts lets each be optimised. A closure that has to roll under a glass flange without cracking wants a soft, ductile metal. A closure that has to snap open at a designed point, identically across a batch, wants a mouldable polymer with a predictable break.

Three consequences follow, and they are why a buyer specifies combi over all-aluminium:

  • Controlled access. A flip-off button exposes a small central injection point while the aluminium stays crimped, so a multi-dose vial can be entered repeatedly without loosening the closure. A tear-down or pull-ring top removes the whole closure instead.
  • Colour and marking. The plastic top holds pigment, embossing and print cleanly, which is how sites differentiate strength on the line. See the colour and marking hub.
  • Tamper evidence at a designed break point. The Optima Button design carries intrinsic tamper evidence through a 12-stem flower moulded under the button disc.

ISO 8362-6 and where combi seals sit

ISO 8362-6 is the part of the ISO 8362 series that covers caps made of aluminium-plastics combinations for injection vials, so it is the direct standard for combi seals. The series covers the whole injection container system, a part at a time:

  • ISO 8362-1: injection vials made of glass tubing, which sets the neck finish a combi seal has to match.
  • ISO 8362-3: aluminium caps for injection vials, the all-aluminium family.
  • ISO 8362-6: the combi seal family, where the plastic part overlaps the aluminium.
  • ISO 8362-7: combination caps without an overlapping plastics part.

Autofits manufactures its combination seals to ISO 8362-6, under an ISO 15378:2017 GMP quality system for primary packaging materials.

The Autofits combi seal range

Design Plastic top How it opens Sizes
FlipTop® Optima PP button disc, in Bridge, Button or Flower design Flip the button up to expose a central injection point; the aluminium stays crimped 13, 20, 28, 32, 34 mm
FlipTop® Pull Ring PP disc with an aluminium pull ring Pull the ring and open anticlockwise; the whole seal detaches once the PP disc is detached 20 mm (bridge), 32 mm (flower)
FlipTop® Tear-Down PP disc riveted to the aluminium Open the disc, then pull and rotate it anticlockwise so the whole seal comes off 13, 20, 32 mm

The Optima is the general-purpose combi seal for injectables and the only design offered across the full size range. Pull Ring seals are often marked for oral use, and Tear-Down is used mainly for oral vaccination presentations.

Specifications and sizing

From the Autofits engineering drawings. Shipper box 420 × 270 × 320 mm. Values not carried on a drawing are shown as on request.

Design and size Inner Ø alu (D1) Outer Ø disc (D2) Disc height Total height Alu thickness Bridges or fins
Optima 13 mm 13.36 min 14.99 max 2.90–3.30 7.62–8.38 0.16–0.20 6 taper
Optima 20 mm 20.22 min 23.14 max 3.20–3.60 9.02–9.91 0.16–0.20 6 taper
Optima 28 mm 27.60–28.20 30.10–31.10 On request 11.06–12.06 0.17–0.23 8
Optima 32 mm 32.10–32.90 35.50–36.50 On request 14.30–15.50 0.21–0.25 12 taper
Optima 34 mm 33.60–34.00 35.50–36.50 On request 15.00–16.00 0.20–0.25 8 taper
Pull Ring 20 mm 20.00–20.60 22.00–23.00 3.00–4.00 9.00–10.00 0.18–0.22 6 taper bridges
Pull Ring 32 mm 32.15–32.40 36.20–36.60 On request 14.30–15.30 0.20–0.26 8 fins (flower)
Tear-Down 13 mm 13.30–13.50 14.80–15.40 3.70–4.10 6.80–8.30 0.18–0.22 Bridge
Tear-Down 20 mm 20.00–20.60 22.00–23.00 3.00–4.00 8.80–9.80 On request Bridge
Tear-Down 32 mm 32.40–33.15 35.70–36.70 On request 14.30–15.30 0.20–0.26 8 fins

All dimensions in millimetres. Maximum opening force is 30 N at 13 mm, 35 N at 20 and 28 mm and 65 N at 32 mm. Standard packing per box is 15,000 at 13 mm (5,000 × 3 bags), 6,000 at 20 mm, 3,000 at 28 mm and 1,400 at 32 mm. Per-size detail sits on the 13 mm, 20 mm and 32 mm pages.

Materials and finishes

The aluminium is alloy AA8011 to EN 15088:2005, supplied with EN 10204 3.1 certification and tested to BS EN 485-2:2008, REACH and RoHS compliant, coated with an epoxy lacquer to 21 CFR 175.300 which may be pigmented for colour. The plastic top is polypropylene to IS 10910 and IS 10909, FDA 21 CFR 177.1520 for olefin polymers and EC 1895/2005, with BADGE, NOGE and BFDGE not used; discs and buttons are moulded in-house on Japanese Toyo injection machines. Heavy metals (chrome-VI, cadmium, mercury, lead) are limited to a maximum 100 ppm total to EN 602 and EC 94/62, and components are BSE/TSE-free to EMEA/410/01 rev. 3.

Finishes are glossy, matte, embossed or printed, in a wide range of colours customised to requirement; aluminium cap finish types covers what each does on the line. Production runs under ISO 15378:2017, ISO 9001:2015 and ISO 14001:2015, with a Drug Master File (DMF 18100) and CFDA registration, with automated washing, ISO Class 8 cleanroom assembly and 100% camera inspection in the 75,000 sq ft Nashik facility. AQL is critical nil, major NMT 2.5%, minor NMT 4%, tailorable. Certificate numbers are on the quality page.

Forms of supply and applications

Combi seals ship Regular (non-sterile), Ready-to-Use or Ready-to-Sterilize. Ready-to-Use seals are washed and assembled in the ISO Class 8 cleanroom, double-lacquered, sterilized by gamma irradiation or ethylene oxide and double-bagged for aseptic areas. Shelf life is 3.5 years before capping for non-irradiated seals, plus 5 years after capping, and 2 years before capping for Ready-to-Use. Tyvek bagging is available. Minimum order quantities, pricing and lead times are available on request.

They cover routine liquid injectables, freeze-dried products, multi-dose vaccines, biologics and oral presentations, and are the default construction wherever colour coding or repeat entry into a multi-dose vial is part of the presentation. To specify, start from the vial neck finish, using the serum vial seals page or the full FlipTop range, then choose the design by opening action.

Frequently asked questions

What is a combi seal?

A combi seal is an aluminium-plastic combination cap for an injection vial: a deep-drawn aluminium shell that crimps under the vial neck flange over the rubber stopper, with a moulded polypropylene top on it. The aluminium holds the sterile barrier by keeping the stopper compressed against the glass; the plastic top provides the opening action, the tamper-evident break point and the surface for colour and printing.

Is a combi seal the same as an aluminium-plastic combination seal?

Yes. Combi seal is the shop-floor short form of the ISO 8362-6 family name, caps made of aluminium-plastics combinations for injection vials. Flip-off, pull-ring and tear-down closures are all combi seals; an all-aluminium tear-off seal is not, because it has no plastic part.

Which ISO standard covers combi seals?

ISO 8362-6, part of the ISO 8362 series on injection containers and accessories, covers caps made of aluminium-plastics combinations for injection vials. ISO 8362-7 covers the variant without an overlapping plastics part. The glass vial neck the cap has to match is defined in ISO 8362-1, and all-aluminium caps sit under ISO 8362-3.

What sizes are combi seals made in?

Autofits makes combi seals in 13, 20, 28, 32 and 34 mm. The flip-off Optima covers all five sizes; Pull Ring is made at 20 mm as a bridge design and 32 mm as a flower design; Tear-Down covers 13, 20 and 32 mm. The size refers to the vial’s neck finish, not its fill volume, and there is no 30 mm size in the range.

Can combi seals be supplied colour coded?

Yes. Colour is applied through pigment in the polypropylene top and, where required, through pigmented epoxy lacquer on the aluminium. Finishes are glossy, matte, embossed or printed, in a wide range of colours customised to requirement. Colour matching, printing and marking are quoted per order.

Related reading

Sources

  • ISO: ISO 8362-6, Injection containers and accessories, Part 6: Caps made of aluminium-plastics combinations for injection vials (https://www.iso.org/)
  • ISO: ISO 8362-7, Injection containers and accessories, Part 7: Injection caps made of aluminium-plastics combinations without overlapping plastics part (https://www.iso.org/)
  • ISO: ISO 8362-1, Injection containers and accessories, Part 1: Injection vials made of glass tubing (https://www.iso.org/)
  • ISO: ISO 15378, Primary packaging materials for medicinal products, GMP requirements (https://www.iso.org/standard/70729.html)
  • Autofits engineering drawings and FlipTop Seals dossier (internal, on file)

*Last updated: 2026-08-18. This page is general technical and product information, not regulatory or compliance advice; confirm current standard editions, material specifications and your own specification with the Autofits technical team and the issuing bodies.*

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