28mm Pharmaceutical Vial Seals & Caps

The 28mm vial cap is the larger-neck closure Autofits supplies as the FlipTop® Optima aluminium-plastic flip-off, crimped over a 28mm rubber stopper to ISO 8362-1. It suits higher-fill injectable and lyophilised vials that need a wider crown bore. At present Autofits stocks the 28mm size as the Optima flip-off; other constructions are available on request. The matrix below gives the dimensions you need to specify the part.

Key takeaways

The 28mm size is currently offered as the FlipTop® Optima flip-off only; other constructions are available on request.
The 28mm Optima inner aluminium diameter is 27.60 to 28.20 mm with a total seal height of 11.06 to 12.06 mm and 8 bridges.
Maximum opening force for the 28mm range is 35 N.
Standard packing is 3,000 seals per box (1,500 x 2 bags), with Tyvek bagging and RTU or RTS delivery available.
The 28mm seal crimps over a 28mm vial neck and stopper to ISO 8362-1.
For the full size index see products by size; for all constructions see the products page.

Which Autofits products come in 28mm

FlipTop® Optima (aluminium-plastic flip-off): a moulded plastic button you flip up to expose a small injection point while the aluminium skirt stays crimped. Available in Bridge, Button, and Flower designs and glossy, matte, embossed, or printed finishes. See FlipTop® Optima 28mm.

Please note: the 28mm size is currently the FlipTop® Optima flip-off only. The all-aluminium tear-off, the tear-down, and the pull-ring constructions are not standard at 28mm, but can be quoted on request. Talk to us about your application and we will advise on feasibility.

28mm product matrix

All dimensions in millimetres, transcribed from the Autofits engineering drawings.

Product	Construction	Inner Ø (D1)	Total height	Alu thickness	How it opens	Product page
FlipTop® Optima	Aluminium-plastic flip-off	27.60–28.20	11.06–12.06	0.17–0.23	Flip plastic button up (8 bridges)	Optima 28mm

Delivery forms and finishes at 28mm

The 28mm Optima is supplied in the same delivery forms as the rest of the range: Regular, Ready-to-Use (RTU, gamma or ETO sterilized), and Ready-to-Sterilize (RTS), double-bagged for aseptic areas. RTU seals are assembled in the ISO Class 8 cleanroom from double-lacquered aluminium, washed to avoid particles, then gamma sterilized. The flip-off button is available in Bridge, Button, and Flower designs, and the aluminium can be glossy, matte, embossed, or printed. The Button design carries intrinsic tamper evidence through a 12-stem flower under the button disc. Non-irradiated stock has a shelf life of 3.5 years before capping; RTU stock is 2 years before capping.

Vial neck and ISO 8362-1 sizing for 28mm

A 28mm seal is specified to the vial neck finish, not to the vial volume. The crown bore, flange diameter, and flange thickness of the glass neck are defined in ISO 8362-1, and a 28mm seal is dimensioned to crimp cleanly over a matched 28mm stopper seated in that neck. The 28mm finish appears on larger injectable and lyophilised vials where a wider crown bore is needed. Always confirm that the seal, the rubber stopper, and the glass vial share the same nominal 28mm neck finish so the crimp seats square and the rolled skirt forms a consistent residual seal force.

Opening force and standard packing for 28mm

From the FlipTop Seals dossier, the 28mm size has a maximum opening force of 35 N. Opening force varies with the number and taper of the bridges, and the 28mm Optima uses 8 bridges.

Standard packing is 3,000 seals per box (1,500 x 2 bags) in a 420 x 270 x 320 mm box. Tyvek bagging is available, and seals can be delivered Regular, Ready-to-Use (RTU, gamma or ETO sterilized), or Ready-to-Sterilize (RTS), double-bagged for aseptic areas. Minimum order quantity, colour selection, and lead times are confirmed on enquiry.

Materials of construction

The 28mm Optima uses the same validated material set as the rest of the FlipTop® range. The shell is aluminium alloy AA8011 (conforming to EN 15088:2005, with EN 10204-3.1 certification and testing to BS EN 485-2:2008; REACH and RoHS compliant), epoxy-lacquer coated to 21 CFR 175.300 and pigmented for colour. The flip-off button is polypropylene moulded to IS 10910 / IS 10909 and FDA 21 CFR 177.1520 for olefin polymers, with BADGE, NOGE, and BFDGE not used. Heavy metals (chrome-VI, cadmium, mercury, lead) are held to a maximum of 100 ppm total per EN 602 and EC 94/62, and the materials are BSE/TSE-free per EMEA/410/01 rev.3.

Quality and standards

28mm seals are produced under the Autofits quality system: ISO 9001:2015, ISO 14001:2015, and ISO 15378:2017 (GMP), supported by a Drug Master File (DMF 18100) and CFDA registration. The aluminium-plastic Optima construction follows ISO 15378:2017 and ISO 8362-6. PP discs are moulded in-house on Japanese Toyo injection machines, washing is fully automated, and every seal passes 100% high-speed camera inspection. Assembly takes place in an ISO Class 8 cleanroom inside the 75,000 sq ft Nashik facility. AQL is critical nil, major NMT 2.5%, minor NMT 4%, and is tailorable. Full certification detail is on the quality page.

Frequently asked questions

What is a 28mm vial cap used for?

A 28mm vial cap is the larger-neck closure used on higher-fill injectable and lyophilised vials that need a wider crown bore. It crimps over a 28mm rubber stopper seated in a 28mm vial neck finish to ISO 8362-1, compressing the stopper against the glass to form the sterile seal. Autofits supplies the 28mm size as the FlipTop® Optima flip-off.

Does Autofits make 28mm tear-off or pull-ring seals?

The 28mm size is currently standard as the FlipTop® Optima flip-off only. The all-aluminium tear-off, the tear-down, and the pull-ring constructions are not standard at 28mm but can be quoted on request. Share your application and we will advise on feasibility.

What is the opening force of a 28mm seal?

The maximum opening force for the 28mm range is 35 N. The 28mm Optima uses 8 bridges, and actual force varies with the taper and count of the bridges in the specific design.

How are 28mm seals packed and delivered?

Standard packing is 3,000 seals per box (1,500 x 2 bags) in a 420 x 270 x 320 mm box. Tyvek bagging is available. Seals can be supplied Regular, Ready-to-Use (gamma or ETO sterilized), or Ready-to-Sterilize, double-bagged for aseptic filling areas.

Are 28mm seals available in different colours?

Yes. The seals are available in a wide range of colours, matte or glossy, customised to requirement, and the aluminium can be printed or embossed. Specific colours and any printing are confirmed at the quotation stage.

Sources

Autofits engineering drawings and FlipTop Seals product dossier (on file).
ISO: ISO 8362-1, Injection containers and accessories, Part 1: Injection vials made of glass tubing (https://www.iso.org/standard/63461.html)
ISO: ISO 15378:2017, Primary packaging materials for medicinal products, GMP requirements (https://www.iso.org/standard/70326.html)

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