Aluminium Pilfer-proof Caps

An Autofits pilfer-proof cap is a roll-on pilfer-proof (ROPP) aluminium closure for threaded bottles, made in five sizes: 22, 25, 28, 35 and 38 mm. Each cap leaves the plant as a smooth aluminium shell with no threads; the threads are rolled into it on the bottle neck during capping, and a lower pilfer band shears on first opening and cannot be reattached. Every size takes an EPE, latex or PVC liner and a plain, printed or chamfered finish, and the range is made in Nashik, India, under ISO 15378.

This page is the index for the range. Each size has its own page with typical containers and specifications, and the liner, finish and capping choices each have a page of their own.

Key takeaways

• A pilfer-proof cap is a roll-on pilfer-proof (ROPP) aluminium screw cap with a tear-off pilfer band that gives permanent, irreversible tamper evidence.
• Autofits makes ROPP caps in 22, 25, 28, 35 and 38 mm, each with its own page below.
• 28 mm is the general-purpose size for pharmaceutical syrups and suspensions; 22 and 25 mm suit smaller bottles, and 35 and 38 mm suit larger and wide-mouth packs.
• Liners: EPE, latex or PVC, chosen per product. Finishes: plain, printed or chamfered, in pigmented lacquer colours.
• The caps are all-aluminium, AA8011 alloy with an epoxy lacquer to 21 CFR 175.300.
• Autofits produces around 250 million aluminium pilfer-proof caps a month, under ISO 9001, ISO 14001 and ISO 15378 with a Drug Master File (DMF 18100).

The ROPP cap range by size

Autofits makes pilfer-proof caps in 22, 25, 28, 35 and 38 mm. The size is the nominal diameter of the bottle’s screw-neck finish the cap is rolled onto, so the size is chosen from the bottle. Container types are typical industry practice, not a limit on use.

All figures in the table are typical values. The controlled drawing for your bottle, including exact shell height and gauge, is confirmed with the quotation, and pack counts, which depend on shell height and liner, are confirmed per order.

What is a pilfer-proof (ROPP) cap?

A pilfer-proof cap is an aluminium screw closure for threaded bottles, designed so that the first opening leaves obvious, irreversible evidence that the seal has been broken. It is almost always a ROPP cap, short for roll-on pilfer-proof, because of how it is applied: the cap is not threaded when it is delivered.

The cap arrives as a plain aluminium shell, a cylinder closed at the top with a sealing liner inside and a knurled skirt, with a lower pilfer band connected to the body by thin bridges across a perforation. During capping, the shell is placed over the bottle neck and forming rollers press the soft aluminium into shape: thread rollers iron the metal into the bottle’s thread profile, and a pilfer roller tucks the lower edge under the retaining bead on the neck.

Because the threads are formed against the actual bottle, the fit is tight and the band is captured beneath the bead. The first time the cap is unscrewed, the band cannot lift over the bead; the bridges shear, and the band stays behind or hangs loose while the cap comes off. The cap itself opens and recloses on its threads like any screw cap, so the container stays reclosable while the tamper evidence is one-time.

For a plain-English primer, see what is a pilfer-proof cap; for the formal definition, see the pilfer-proof cap glossary entry.

Choosing the size: start from the bottle

The cap follows the bottle, and the bottle follows the product and the dose. In practice the selection runs in this order:

1. Fix the container. Fill volume, dosing method and whether a wider neck is needed for powder filling or reconstitution determine the bottle and its neck finish.
2. Read the neck finish from the bottle drawing. Nominal diameter gives the cap size. Thread pitch, bead diameter and neck height confirm the cap profile, because two bottles of the same nominal size can differ in all three.
3. Confirm the capping equipment. Roll-on capping heads are set up per size, so a size change is a changeover. Lines that run several products often standardise on one neck finish, usually 28 mm.
4. Select the liner for the product. See ROPP cap liners.
5. Select the finish and any colour or print. See ROPP cap finishes.

If the container is a stoppered injectable vial rather than a threaded bottle, a ROPP cap is the wrong closure family. Vials take a crimped seal; see pilfer-proof cap vs flip-off seal.

Liners, finishes and capping

Size is one of four choices made together: size, liner, finish and how the caps are supplied. Each of the other three has its own page.

The liner does the sealing. The rolled aluminium holds it in compression against the flat land at the top of the bottle neck, and the pilfer band carries the tamper evidence. A correct shell with the wrong liner will still leak, which is why the liner is chosen by compatibility study rather than by size.

Materials

The Autofits pilfer-proof cap is an all-aluminium closure with an epoxy lacquer lining, selected and tested for pharmaceutical packaging duty. It carries no plastic component in the shell; the tamper evidence is built into the aluminium itself.

• Aluminium: alloy AA8011, conforming to EN 15088:2005, supplied with EN 10204 3.1 certification and tested to BS EN 485-2:2008. REACH and RoHS compliant. Gauge is typically 0.20 to 0.25 mm, heavier on the larger sizes, as in the table above.
• Lacquer: epoxy lacquer coating conforming to 21 CFR 175.300; it may be pigmented for colour.
• Heavy metals: chrome-VI, cadmium, mercury and lead held to a maximum 100 ppm total (EN 602, EC 94/62).
• BSE/TSE-free: per EMEA/410/01 rev. 3.

These material declarations are the ones Autofits documents for its aluminium seal range; the declarations for a specific cap, liner and finish are supplied with the quotation.

Manufacturing and quality

Pilfer-proof caps are produced under an ISO 15378:2017 GMP quality system, with online high-speed camera inspection. Production runs in the Autofits Packaging Pvt. Ltd. 75,000 sq ft facility in Nashik, India, which also houses an ISO Class 8 cleanroom and in-house design and development. Output is around 250 million aluminium pilfer-proof caps a month, alongside more than 2.4 billion seals a year.

• Quality system: ISO 9001:2015, ISO 14001:2015 and ISO 15378:2017 (GMP for primary packaging materials); see ISO 15378.
• Regulatory filings: Drug Master File (DMF 18100) and CFDA registration.
• Acceptance sampling: the AQL plan for a cap order is agreed to the customer’s specification, on top of the camera inspection.

The full certification set is on the quality page.

Supply and packing

Pilfer-proof caps ship bulk packed in cartons, with the pack count per carton depending on size, shell height and liner. Typical counts run from about 12,000 caps at 22 mm to about 4,000 at 38 mm, as in the size table, and are confirmed per order.

The Regular, Ready-to-Use and Ready-to-Sterilize forms that Autofits documents for its vial seals are built for sterile injectable lines. Pilfer-proof caps close oral liquids, powders and reagents, which are normally filled in clean rather than aseptic conditions, so if a line needs washed or sterilised caps, the presentation and its documentation are confirmed on enquiry.

Applications

Pilfer-proof caps suit any threaded pharmaceutical bottle that needs visible, irreversible tamper evidence and a reclosable cap. Typical uses include:

• Oral liquids, syrups and suspensions, the core use, from small paediatric bottles at 25 mm to general-purpose 28 mm bottles.
• Dry syrups and powders for reconstitution, where a wider 35 or 38 mm neck eases powder filling on larger packs.
• Diagnostics and reagent bottles, including research-use reagents, often at 22 mm.
• Veterinary oral and topical liquids in screw-neck bottles.

Injectable vials take crimped flip-off seals rather than threaded caps; for those, see the FlipTop aluminium-plastic seals, in particular the FlipTop Optima flip-off seal, and the applications hub.

How pilfer-proof caps compare with flip-off vial seals

A pilfer-proof cap is a threaded, reclosable screw cap for bottles; a flip-off seal is a crimped, single-access seal for injectable vials. Both are aluminium-based and both give tamper evidence, but they close different containers in different ways.

Ordering

Send the bottle neck finish drawing, size, liner, finish, colour reference and any print artwork, and the matching cap drawing comes back with the quotation. Autofits holds standard designs that are available with minimal lead time, customises finish, print and liner to requirement, and supplies more than 150 pharmaceutical companies.

As a guide, standard designs are typically ordered from 50,000 pieces per size and colour with a typical lead time of 2 to 3 weeks from order confirmation; custom colour or print typically starts at 100,000 pieces and takes 4 to 6 weeks including artwork approval. Both are confirmed with the quotation. Contact Autofits with your specification.

Frequently asked questions

What is a pilfer-proof cap?

A pilfer-proof cap is an aluminium screw cap for threaded bottles with a tear-off band at its base that breaks the first time the container is opened, giving permanent tamper evidence. It is usually a ROPP (roll-on pilfer-proof) cap, supplied as a smooth threadless shell whose threads are formed onto the bottle neck during capping. A broken or missing band shows that the container has been opened.

What does ROPP stand for?

ROPP stands for roll-on pilfer-proof. It describes an aluminium cap supplied as a plain threadless shell that has its threads rolled, or formed, directly onto the bottle neck during capping, while the tamper-evident pilfer band is locked under the bottle bead at the same time.

What sizes do Autofits pilfer-proof caps come in?

Autofits makes pilfer-proof (ROPP) caps in five sizes: 22, 25, 28, 35 and 38 mm. The size is the nominal diameter of the bottle’s screw-neck finish. The controlled drawing for a specific bottle, including exact shell height, is confirmed with the quotation, because neck finishes of the same nominal size can differ in thread pitch and bead position.

Which ROPP cap size is most common in pharma?

28 mm is the general-purpose size for pharmaceutical syrups and suspensions, and lines that run several products often standardise on it to avoid capping changeovers. 22 and 25 mm suit smaller bottles such as drops and paediatric syrups, and 35 and 38 mm suit dry syrups, larger packs and wide-mouth bottles.

Is a pilfer-proof cap reclosable?

Yes. Because the threads are formed onto the bottle, a pilfer-proof cap screws back on after opening and the liner reseals the container. The tamper evidence is one-time: once the band has broken on first opening it stays broken, but the cap itself can be removed and replaced like any screw cap.

What liners are available in Autofits pilfer-proof caps?

EPE, latex and PVC liners are available across the size range. EPE is a one-piece expanded polyethylene foam and the usual starting point for aqueous oral liquids. Latex and PVC liners are used where the formulation or closing process suits them. The choice is confirmed by a compatibility and leak study on the filled pack.

Can the caps be coloured or printed?

Yes. Pilfer-proof caps are available in plain, printed and chamfered finishes. Colour comes from pigmenting the epoxy lacquer, and artwork is printed while the aluminium is still flat, before the shell is formed. Send a colour reference and any artwork with your enquiry.

Are 13, 20 and 32 mm pilfer-proof caps available?

Those are vial seal sizes, not ROPP sizes. 13, 20, 28, 32 and 34 mm are the diameters of the Autofits crimped aluminium and aluminium-plastic vial seals, which close stoppered injectable vials rather than threaded bottles. The pilfer-proof range runs 22 to 38 mm.

Related reading

• 22mm ROPP cap
• 25mm ROPP cap
• 28mm ROPP cap
• 35mm ROPP cap
• 38mm ROPP cap
• ROPP cap liners: EPE, latex and PVC
• ROPP cap finishes: plain, printed and chamfered
• Applying ROPP caps: roll-on capping and torque
• All Autofits products

Sources

• Autofits seal product dossier (material declarations)
• ISO: ISO 15378:2017, Primary packaging materials for medicinal products, GMP requirements (https://www.iso.org/standard/70729.html)
• eCFR: 21 CFR 175.300, Resinous and polymeric coatings (https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-175/subpart-C/section-175.300)
• Autofits Packaging Pvt. Ltd.: company brochure, sizes, liners, finishes and capacity (https://autofits.com/wp-content/uploads/2024/07/Autofits-Brochure.pdf)

*Last updated: 2026-09-15. This page is general technical and product information, not regulatory or compliance advice; typical values are indicative, and the controlled drawing for your bottle is confirmed with the quotation.*