Ready-to-Use and Ready-to-Sterilise Vial Seals
Autofits supplies its FlipTop® vial seals in three delivery forms: Regular, Ready-to-Sterilise (RTS) and Ready-to-Use (RTU). Ready-to-Use seals are washed, assembled in an ISO Class 8 cleanroom, double-lacquered, sterilised by gamma irradiation or ethylene oxide (ETO) and double-bagged so they can go into an aseptic filling area. Ready-to-Sterilise seals arrive clean and packed for the drug maker’s own sterilisation cycle. Both forms are offered on the FlipTop Optima, Pull Ring and Tear-Down lines from 13 to 34 mm.
Key takeaways
- Three delivery forms: Regular, Ready-to-Sterilise (RTS) and Ready-to-Use (RTU).
- RTU sterilisation: gamma irradiation or ETO, after cleanroom assembly.
- Assembly: ISO Class 8 cleanroom, with fully automated washing to remove particles.
- Packing: double-bagged for aseptic areas; Tyvek bagging available.
- Shelf life before capping: 2 years for RTU seals; 3.5 years for non-irradiated seals, plus 5 years after capping.
- Lines: FlipTop Optima (13, 20, 28, 32, 34 mm), Pull Ring (20, 32 mm) and Tear-Down (13, 20, 32 mm).
What ready-to-use and ready-to-sterilise mean
A ready-to-use seal is sterile on arrival and goes onto the filling line without further treatment; a ready-to-sterilise seal is clean on arrival and is sterilised by the drug maker before use. The difference decides who owns the sterilisation step, and so whose validation covers it.
With RTU seals, the seal maker carries out washing, cleanroom assembly and sterilisation, and the filling site receives a component it can transfer into the aseptic area through its own entry procedure. With RTS seals, the filling site runs the sterilisation in its own validated cycle, which suits sites that already sterilise stoppers and other components in house. Regular seals are the standard industrial form, used where the seal is crimped outside the aseptic core or where the site has its own preparation process.
EU GMP Annex 1 requires components entering a Grade A area to be sterilised by a validated process and transferred in a way that keeps them sterile, which is why the delivery form is chosen together with the site’s contamination control strategy. How Annex 1 treats components is set out on the EU GMP Annex 1 page.
The three delivery forms side by side
| Regular | Ready-to-Sterilise (RTS) | Ready-to-Use (RTU) | |
|---|---|---|---|
| State on arrival | Clean, inspected | Clean, packed for sterilisation | Sterile |
| Who sterilises | Not sterilised | The drug maker, in its own cycle | Autofits, by gamma or ETO |
| Washing | Fully automated | Fully automated | Fully automated, to remove particles |
| Assembly | Automated line | Automated line | ISO Class 8 cleanroom |
| Aluminium | Lacquered | Lacquered | Double-lacquered |
| Packing | Standard bags in the box; Tyvek on request | Confirmed with the specification; Tyvek available | Double-bagged for aseptic areas |
| Shelf life before capping | 3.5 years (non-irradiated), plus 5 years after capping | Confirmed with the specification | 2 years |
Every form passes the same 100% high-speed camera inspection before packing.
How a ready-to-use seal is made
RTU seals follow the standard FlipTop process with three added controls: cleanroom assembly, a second lacquer coat and terminal sterilisation of the packed seal.
- The aluminium shell is formed from AA8011 alloy and double-lacquered with an epoxy lacquer that conforms to 21 CFR 175.300.
- The polypropylene disc is moulded in house on Japanese Toyo injection machines.
- Components are washed on a fully automated line so loose particles are removed before assembly.
- Shell and disc are assembled in an ISO Class 8 cleanroom.
- Every seal passes high-speed camera inspection.
- Seals are double-bagged and sterilised by gamma irradiation or ETO.
Gamma irradiation is validated under ISO 11137 and ethylene oxide under ISO 11135. Which method suits a given seal and how a buyer reviews the validation is covered on the sterilisation validation page, and the cleanroom sealing environment on sterile vial sealing.
Which lines and sizes come in each form
All three delivery forms are offered across the FlipTop aluminium-plastic range.
| Line | Sizes | Regular | RTS | RTU |
|---|---|---|---|---|
| FlipTop® Optima | 13, 20, 28, 32, 34 mm | Yes | Yes | Yes |
| FlipTop® Pull Ring | 20, 32 mm | Yes | Yes | Yes |
| FlipTop® Tear-Down | 13, 20, 32 mm | Yes | Yes | Yes |
For the all-aluminium tear-off seals and tear-down seals, the delivery form is confirmed with the quotation.
Packing for the aseptic area
RTU seals are double-bagged so the outer bag can be removed at the clean-area boundary and the inner bag carried in. Tyvek bagging is available where a breathable bag is specified, which matters most for RTS seals that are sterilised through the bag. Bags are packed in the standard shipper box of 420 × 270 × 320 mm; counts per box by size are on the packaging and shipping page.
In practice at Autofits
RTU and RTS seals come off the same Nashik lines as Regular seals, under the same ISO 15378:2017 quality system, so a buyer qualifying one form is auditing the same process for all three. The cleanroom, washing and inspection steps are described on the quality page and the plant on the factory page.
Frequently asked questions
What is a ready-to-use vial seal?
A ready-to-use (RTU) vial seal is supplied sterile, so it can go onto an aseptic filling line without further treatment by the drug maker. Autofits RTU seals are washed, assembled in an ISO Class 8 cleanroom, double-lacquered, sterilised by gamma irradiation or ETO and double-bagged.
What is the difference between RTU and RTS seals?
RTU seals are sterilised by the seal maker and arrive sterile. RTS (ready-to-sterilise) seals arrive clean and packed so the drug maker can sterilise them in its own validated cycle. The choice decides whose validation covers the sterilisation step.
How are ready-to-use flip-off seals sterilised?
Autofits sterilises RTU seals by gamma irradiation or by ethylene oxide (ETO), after cleanroom assembly and double bagging. The method is chosen with the buyer and stated in the specification.
What is the shelf life of ready-to-use seals?
Ready-to-use seals have a shelf life of 2 years before capping. Non-irradiated seals have 3.5 years before capping, plus 5 years after capping.
Which Autofits seals are available ready to use?
FlipTop Optima seals from 13 to 34 mm, FlipTop Pull Ring seals at 20 and 32 mm and FlipTop Tear-Down seals at 13, 20 and 32 mm are available in RTU and RTS form. For all-aluminium tear-off and tear-down seals the delivery form is confirmed with the quotation.
Sources
- European Commission: EudraLex Volume 4, Annex 1, Manufacture of Sterile Medicinal Products
- ISO: ISO 11137, Sterilization of health care products, Radiation; ISO 11135, Ethylene oxide (iso.org)
- Autofits FlipTop Seals dossier and engineering drawings
*Last updated: 2026-11-06. Product information only, not regulatory advice. Delivery form, packing and sterilisation method are confirmed with the quotation.*
