Flip-Off vs Flip-Up Seal: Are They the Same Vial Closure?

On an injectable vial, flip-off and flip-up describe the same closure: an aluminium-plastics combination cap whose moulded plastic button is lifted by thumb to expose the centre of the rubber stopper, while the aluminium skirt stays crimped on the vial neck. There is no separate ISO category for a flip-up seal. The two words describe the same action from different ends: the button flips up, and in doing so it comes off. The distinction only becomes real outside injectable vials, where a flip-up or flip-top cap usually means a hinged dispensing closure on a plastic bottle, which is not a vial seal at all.

This page sets out where the two terms overlap, where they genuinely diverge, which standards actually define the closure, and what a buyer should specify instead of arguing about the name.

Key takeaways

Same closure, two words. In injectable vial packaging, flip-off and flip-up are used interchangeably for an aluminium shell crimped over a rubber stopper with a moulded plastic top.
The formal category is standards-defined. ISO 8362-6 covers caps made of aluminium-plastics combinations for injection vials, and ISO 8362-7 covers the version without an overlapping plastics part. Neither standard uses the words flip-off or flip-up.
Flip-up emphasises the motion, flip-off emphasises the outcome. On most designs the button lifts on shearing bridges and then separates.
A real difference does exist outside vials: a flip-top or flip-up cap on a plastic bottle is a hinged dispensing closure, not a crimped sterile-barrier seal.
Specify the design, not the nickname. Bridge, button, and flower tops behave differently on the line and in the hand, so the sub-type matters far more than the word used.
Flip-Off is a registered trademark of West Pharmaceutical Services, Inc. Autofits products in this category are branded FlipTop, and Autofits is not affiliated with West.

Why buyers see both terms

Both terms exist because the closure does two things in one movement, and different markets latched onto different halves of it. The user’s thumb pushes the edge of the plastic disc upward, the small bridges holding the disc shear, and the disc leaves the cap. Describe the gesture and you get flip-up. Describe the result and you get flip-off. Catalogues, tenders, and lab SOPs use both, along with flip-top, flip cap, and tear-open cap.

Because none of these are standardised terms, the safest way to identify a closure in an enquiry is by its construction and neck size: an aluminium-plastics combination cap for a 20 mm injection vial, for example. That description maps directly onto a standard and onto a vial neck finish, which a nickname does not. The underlying part is described in the aluminium-plastic seal and flip-off seal glossary entries.

What actually varies between designs

Where a genuine difference exists, it is in the top design and in whether the plastic overlaps the aluminium, not in the choice between the words flip-off and flip-up. Three variables change how a seal feels when it is opened.

The first is the bridge arrangement. The plastic disc is attached to the plastic ring by small bridges that shear when the button is flipped. The number and taper of those bridges set the opening force, so a 13 mm seal and a 32 mm seal do not open with the same effort even though both are flip-off caps. The second is whether the plastic part overlaps the aluminium skirt. ISO 8362-7 exists precisely because some combination caps leave the aluminium exposed at the shoulder rather than covering it, which changes the look and the way the part is gripped. The third is the top geometry itself: bridge, button, and flower tops present different surfaces to the thumb and to a camera on the inspection line. Those differences are compared in detail in bridge type vs button type.

Flip-off vs flip-up: the comparison

The table separates what is the same from what is different, including the non-vial case where the words really do point at two different products.

Attribute	Flip-off seal (injectable vial)	Flip-up seal (injectable vial)	Flip-up / flip-top cap (bottle)
What it names	The plastic button detaching	The plastic button lifting	A hinged dispensing lid
Underlying product	Aluminium-plastics combination cap	The same aluminium-plastics combination cap	Moulded plastic closure, no aluminium
Governing standard	ISO 8362-6 / ISO 8362-7	ISO 8362-6 / ISO 8362-7	Not a vial seal standard
Sealing principle	Aluminium skirt crimped over a rubber stopper	Aluminium skirt crimped over a rubber stopper	Threaded or snap fit onto a bottle neck
What remains after opening	Crimped aluminium skirt on the neck	Crimped aluminium skirt on the neck	The whole cap, hinged open
Sterile barrier	Yes, maintained by the crimp and stopper	Yes, maintained by the crimp and stopper	No
Tamper evidence	Detached button plus intact factory crimp	Detached button plus intact factory crimp	Usually a separate tamper band
Reclosable	No	No	Yes
Typical contents	Injectables, vaccines, diluents	Injectables, vaccines, diluents	Oral liquids, topicals, consumer products

The first two columns are identical on every line that matters, which is the point. The third column is the only place where a buyer who says flip-up might mean something genuinely different, and it is easy to rule out by asking whether the container is a stoppered vial or a threaded bottle.

How to write the enquiry so nothing is lost

Give the vial neck size, the stopper it has to work with, the top design, the finish and colour, and the supply form. A request for two million 20 mm flip-up seals is ambiguous on four of those five points. A request for two million 20 mm aluminium-plastics combination caps to ISO 8362-6, bridge top, matte finish in a specified colour, supplied ready to use, is not.

Matching the seal to the vial and the stopper is the part that carries real risk. The seal diameter follows the vial neck finish, and vial necks follow ISO 8362-1, so a nominal 20 mm seal belongs on a 20 mm neck with a 20 mm stopper. The mechanism itself is covered in how flip-off caps work.

How this works in practice at Autofits

Autofits calls this closure family FlipTop, and the general-purpose member of it is the FlipTop Optima. It is an AA8011 aluminium shell with an epoxy lacquer coating and an injection-moulded polypropylene button, made in 13, 20, 28, 32 and 34 mm neck sizes, with Bridge, Button and Flower top designs, in glossy, matte, embossed or printed finishes. Maximum opening force is specified per size, from 30 N on the 13 mm to 65 N on the 32 mm, which is the number that actually determines whether a seal feels like it flips up easily or not. Production runs under ISO 9001:2015, ISO 14001:2015 and ISO 15378:2017 with Drug Master File 18100, in a 75,000 sq ft Nashik facility with an ISO Class 8 cleanroom and 100% high-speed camera inspection. The certificate set is on the quality page.

If you are writing an enquiry rather than settling terminology, it is faster to start from the drug product. The vial sealing applications hub maps each category to the closure that fits, and the two highest-volume cases, multidose vaccine vial seals and IV diluent and saline closures, between them account for most flip-off enquiries that arrive here.

Frequently asked questions

Is a flip-up seal the same as a flip-off seal?

For injectable vials, yes. Both names describe an aluminium-plastics combination cap crimped over a rubber stopper, with a moulded plastic button that the user lifts to expose the centre of the stopper for a needle. The aluminium skirt stays crimped on the vial in both cases. There is no separate product category, standard, or dimensional specification for a flip-up seal.

Is there an ISO standard for a flip-up seal?

Not under that name. ISO 8362-6 specifies caps made of aluminium-plastics combinations for injection vials, and ISO 8362-7 specifies the variant without an overlapping plastics part. All-aluminium caps without a plastic top fall under ISO 8362-3. A supplier quoting to one of those parts is quoting to the closure that buyers call flip-off or flip-up.

Does the plastic button stay attached after it is flipped?

On most designs it does not. The disc is held by small bridges that shear when it is lifted, so the disc separates and is discarded, leaving the crimped aluminium skirt and the exposed stopper. The number and taper of the bridges set the opening force, which is specified per seal size.

What is the difference between a flip-top vial seal and a flip-top bottle cap?

They are unrelated closures. A flip-top vial seal is an aluminium-plastics cap crimped over a stopper to hold a sterile barrier on an injectable vial. A flip-top bottle cap is a moulded plastic dispensing closure with a hinged lid, fitted to a threaded or snap-fit bottle neck, and it is reclosable. Only the first maintains container closure integrity on a parenteral product.

Which term should I use in a purchase specification?

Use the construction and the standard rather than the nickname: an aluminium-plastics combination cap to ISO 8362-6, with the neck size, top design, finish, colour, and supply form stated. Nicknames vary between markets and suppliers, while the standard reference and the neck size do not.

Sources

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)
ISO: ISO 8362-7:2006, Injection containers and accessories, Part 7: Injection caps made of aluminium-plastics combinations without overlapping plastics part (https://www.iso.org/standard/43551.html)
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)
West Pharmaceutical Services: Seals product family and trademark notice (https://www.westpharma.com/products/vial-containment-solutions/seals)

*Last updated: 2026-07-31. This article is general technical information about pharmaceutical vial closures, not regulatory or compliance advice; confirm current standard editions and product specifications with the relevant body and your supplier. Flip-Off is a registered trademark of West Pharmaceutical Services, Inc., used here only to identify that company’s products.*