Polymer vs Glass Vial: Crystal Zenith and What Changes at the Closure
Choosing between a polymer and a glass vial is a container decision that comes before the closure decision. Crystal Zenith vials are moulded from cyclic olefin polymer (COP), a Daikyo Seiko technology sold by West Pharmaceutical Services for products where glass breaks, delaminates or loses integrity at very low temperature. A glass injection vial is typically Type I borosilicate, made to ISO 8362-1 or ISO 8362-4 and tested under USP <660>. West states that its Crystal Zenith vials are made to the exterior dimensions of ISO 8362-1, so they can take a crimped stopper and aluminium seal; what changes is the material file, the chapters that apply, and the capping and integrity data, which have to be established on the polymer vial rather than carried over from glass.
Key takeaways
- Crystal Zenith is a container material, not a closure. It is a cyclic olefin polymer; Crystal Zenith is a trademark of Daikyo Seiko, Ltd., and the technology is licensed to West.
- Glass remains the default. Type I borosilicate vials are made to ISO 8362-1 (tubing) or ISO 8362-4 (moulded) and evaluated under USP <660>.
- Different chapters apply. Plastic packaging systems are assessed under USP <661.1> and <661.2> rather than the glass chapter.
- The reasons to move are specific: breakage, delamination, viral vector recovery and cryogenic storage, where West states that COP expands and contracts more like an elastomer than glass does.
- Two closure routes exist. West lists press-fit PLASCAP closures, or a stopper crimped with an aluminium seal, for its Crystal Zenith vials.
- Crimp settings and integrity data do not transfer. A polymer neck responds to crimp force differently from glass, so both are re-established on the actual combination.
What Crystal Zenith is
Crystal Zenith is a cyclic olefin polymer moulded into vials and syringes and positioned as an alternative to glass for sensitive products. West’s Crystal Zenith page describes glass-like transparency, break resistance and minimal chemical interaction risk, and positions the vials for advanced therapies and sensitive molecules facing delamination, light sensitivity, viral vector recovery and particulates.
The published range runs from 2 mL to 100 mL, including 2 mL and 10 mL nested vials in tubs and a 25 mL light-protection version. West’s dimension tables give a crown outer diameter of 13.00 mm on the 2 mL nested vial and 20.00 mm on the 10 mL nested vial, which are the two commonest seal sizes on glass. West also states proven container closure integrity at minus 80 °C and at cryogenic temperature, minus 190 °C, for its own systems.
None of this is a new sealing mechanism. The container material changes; holding the sterile barrier is still the job of the stopper and whatever retains it, as set out in container closure system.
What glass still does well
Type I borosilicate glass is the reference material for parenteral containers, with a long regulatory history, well-characterised chemistry and a supply base at every scale. It is dimensionally stable, effectively impermeable to gases and moisture, and its behaviour under crimping is well understood, which is why capping data and integrity models for glass are mature. Neck finishes follow ISO 8362-1 for tubing vials and ISO 8362-4 for moulded vials, so stoppers and seals of the same nominal size interchange predictably across suppliers.
Glass has two failure modes that drive the polymer conversation. It breaks, which matters most in cryogenic handling and distribution. And under some formulation and process conditions its inner surface can delaminate and shed flakes. Both are container problems, and both are what a polymer vial is chosen to avoid.
Polymer vs glass: the comparison
The table compares the containers first, then what carries over to the closure.
| Attribute | Crystal Zenith (COP) vial | Type I glass vial |
|---|---|---|
| Material | Cyclic olefin polymer, moulded | Borosilicate glass, tubing or moulded |
| Supply | Licensed technology from Daikyo Seiko, sold by West | Generic material, many manufacturers |
| Container standards | USP <661.1> and <661.2>; exterior dimensions to ISO 8362-1, per West | ISO 8362-1 or ISO 8362-4; USP <660> |
| Break resistance | High, a primary reason for selection | Brittle; breakage is a handling risk |
| Delamination | Not a glass delamination mechanism | A known risk under some formulation and process conditions |
| Low-temperature behaviour | West states COP’s thermal expansion is closer to elastomers, reducing gap risk | Larger mismatch with the stopper at cryogenic temperature |
| Gas and moisture barrier | Assessed per product | Effectively impermeable |
| Extractables and leachables | Polymer profile, assessed as a plastic system | Glass profile, plus any surface treatment |
| Sizes | 2 mL to 100 mL listed by West | Wide range from many suppliers |
| Closure routes | Press-fit PLASCAP, or stopper plus crimped seal | Stopper plus crimped seal |
| Capping parameters | Established for the polymer neck | Well established |
| Unit cost | Quoted per programme; not compared here | Quoted per programme; not compared here |
What changes at the closure
Four things need attention when a product moves from glass to polymer, and the seal drawing is not one of them.
Crimp force and capping set-up. The aluminium skirt is rolled under the neck flange and compresses the stopper against the container. Glass resists that as a rigid body; a moulded polymer neck has different stiffness and creep, so the residual seal force at a given capper setting will not necessarily match. The capping station has to be set up and challenged on the polymer vial itself.
Integrity evidence. Integrity is a property of the assembled vial, stopper and seal, so it is demonstrated on that combination across the storage and shipping conditions the product will see, including any cryogenic hold. USP <1207> sets out the method families, and EU GMP Annex 1 expects crimped containers to be sampled and checked with validated methods under a scientifically justified sampling plan.
The material file. A polymer container is assessed as a plastic packaging system, with a different extractables and leachables position and a different set of USP chapters from glass. That assessment sits with the container supplier’s data and your own product study.
Silicone and the stopper. Silicone oil in a vial system comes mostly from stopper siliconisation, although some glass vials are siliconised too, so switching to a polymer vial does not by itself remove it. Datwyler, for example, describes its fluoropolymer-coated stoppers as reducing the need for added silicone oil, which is a stopper choice made separately from the container. The stopper component itself is defined under elastomeric closure.
When each choice makes sense
Choose glass unless there is a specific reason not to, and choose a polymer vial when that reason is breakage, delamination, low-temperature integrity or recovery of a low-concentration product. Glass carries the deepest regulatory history, the widest supply base and the most mature capping knowledge, and most conventional small-molecule injectables have no driver to move.
A polymer vial earns its place for a cell or gene therapy held frozen, where breakage in handling has real consequences, where a formulation has shown delamination sensitivity, or where product lost to the container surface matters. West’s published study of two AAV serotypes in 2 mL vials reported higher viral titre recovery in Crystal Zenith than in two borosilicate glass comparators, and West notes that each drug maker has to confirm the result with its own product. For cold-chain closure choices generally, see vial closures for cold chain drugs.
How this works in practice at Autofits
Autofits specifies its seals against the vial neck finish rather than the container material. The FlipTop Optima is drawn to controlled dimensions in 13, 20, 28, 32 and 34 mm, following ISO 8362-6, with vial necks to ISO 8362-1; all-aluminium tear-off and tear-down seals follow ISO 8362-3. Autofits does not make stoppers or containers, so the stopper comes from the buyer’s stopper supplier and the seal is matched to it by nominal size. For any polymer or non-standard neck, the crown is checked against the controlled seal drawing before a trial, and capping settings and integrity data are established on the actual container. Production runs under ISO 15378:2017 with Drug Master File 18100; certificates are on the quality page.
Frequently asked questions
What is Crystal Zenith made of?
Crystal Zenith is a cyclic olefin polymer, a clear thermoplastic moulded into primary containers such as vials and syringe barrels. Crystal Zenith is a trademark of Daikyo Seiko, Ltd., and West Pharmaceutical Services sells Crystal Zenith vials under licence from Daikyo Seiko.
Do polymer vials use the same stoppers and seals as glass vials?
They can. West states that its Crystal Zenith vials meet the exterior dimensions of ISO 8362-1 and can be closed by crimping a stopper with an aluminium seal, or with a press-fit PLASCAP closure. Where a crimped seal is used, capping parameters are re-established, because a moulded polymer neck responds to crimp force differently from glass.
Why would a product move from glass to a polymer vial?
The usual drivers are breakage, delamination, product recovery and cryogenic storage. Polymer vials resist breakage, they do not delaminate the way glass can, and West states that cyclic olefin polymer has a coefficient of thermal expansion closer to elastomers than glass has, which reduces the risk of gaps between vial and stopper at very low temperature.
Which standards apply to each container type?
Glass injection vials are made to ISO 8362-1 for tubing vials or ISO 8362-4 for moulded vials and evaluated under USP General Chapter <660>. Plastic packaging systems, including polymer vials, are evaluated under USP <661.1> for materials of construction and USP <661.2> for the packaging system. The stopper is covered by ISO 8362-2 and the cap by ISO 8362-3 or ISO 8362-6.
Does a polymer vial need different container closure integrity testing?
The method families are the same, but glass data cannot be carried over. Integrity has to be shown on the actual vial, stopper and seal across the storage and transport conditions the product will see, including any frozen hold. USP <1207> describes deterministic and probabilistic methods, and EU GMP Annex 1 expects validated methods and a justified sampling plan for crimped containers.
Related reading
Sources
- West Pharmaceutical Services: Daikyo Crystal Zenith vials, including sizes, dimensions, closure options and trademark notice (https://www.westpharma.com/products/vial-containment-solutions/vials/daikyo-crystal-zenith-cyclic-olefin-polymer-vials)
- West Pharmaceutical Services: Storage of cell therapies, advantages of cyclic olefin polymer vials, 30 October 2020 (https://www.westpharma.com/blog/2020/october/storage-of-cell-therapies-advantages-of-cyclic-olefin-polymer-vials)
- West Pharmaceutical Services: Maintaining viral vector recovery using Daikyo Crystal Zenith vials (https://www.westpharma.com/blog/2024/august/daikyo-cz-vs-borosilicate-glass-aav-stability-cell-gene-therapy)
- ISO: ISO 8362-1:2018, Injection vials made of glass tubing (https://www.iso.org/standard/74398.html)
- ISO: ISO 8362-4:2011, Injection vials made of moulded glass (https://www.iso.org/standard/57745.html)
- European Commission: EU GMP Guidelines, Annex 1, Manufacture of Sterile Medicinal Products, sections 8.21 to 8.26 (https://health.ec.europa.eu/medicinal-products/eudralex/eudralex-volume-4_en)
- USP: General Chapters <660>, <661.1>, <661.2> and <1207> (https://www.usp.org)
- Datwyler Healthcare: Vial stoppers and caps, for OmniFlex coated stoppers and silicone oil (https://healthcare.datwyler.com/resources/sealing-solutions-vials)
*Last updated: 2026-09-15. This article is general technical information about pharmaceutical containers and closures, not regulatory advice; confirm current standard editions and container specifications with the issuing body and your supplier. Crystal Zenith and PLASCAP are trademarks of Daikyo Seiko, Ltd.; the vials referenced are sold by West Pharmaceutical Services, Inc. Both are named only to identify those companies’ products, and Autofits is not affiliated with either.*
