Bottle Neck Finishes and Closure Compatibility

A finish designation such as 28-400 has two parts. The first number is the nominal neck diameter in millimeters (the T dimension, measured across the threads). The second number identifies the thread style under the Glass Packaging Institute (GPI) and Society of the Plastics Industry (SPI) convention. Both parts must match between bottle and closure. A matching diameter alone does not make a closure fit.

Even a matching designation does not prove the package works. Liner, sealing surface, closure material, fill temperature, product and capping process all affect whether the closure seals and opens as intended. Treat the designation as a first screen, then confirm with drawings, samples and application tests. The sections below cover how to read finish documents and how compatibility is checked.

Reading a finish designation

For continuous-thread finishes, two distributors’ guides describe the same convention. The Cary Company explains that the neck width (T) and the thread style are the two critical factors, written as a two-digit number and a three-digit number separated by a dash or slash, such as 28-410. Paramount Global gives the common thread styles: 400 is one thread turn, 410 is one and a half turns, and 415 is two turns with thinner threads and a typically taller neck. Both guides state that GPI and SPI created the guidelines for threading on glass and plastic containers respectively.

What T, E, I, H and S mean

Both guides define the same five dimensions, which you can use to read a drawing or to ask a supplier for one.

Dimension	Definition	Why it matters
T	Outside diameter including the thread	The nominal size in the designation; determines the closure counterpart
E	Outside diameter of the neck without the thread	The difference between T and E, divided by two, gives thread depth
I	Inside diameter of the neck	Needed for filling-tube clearance, plug seals, orifice reducers and fitments
S	From the top of the finish to the top edge of the first thread	Sets closure orientation and the amount of thread engagement
H	Finish height, from the top of the neck to where T extended down meets the shoulder	Separates finishes with similar diameters

This guide gives no numeric values for these dimensions. Distributor tables differ in H and I and in tolerances, so use the current drawing from the glass maker or the standard itself.

Finish families

Finishes are grouped by how the closure attaches and seals. The table lists the families most buyers meet.

Family	How it attaches and seals	Documents to ask for
Continuous thread (CT)	Closure screws on a continuous thread; seal is usually on the top of the finish through a liner	GPI finish designation, or a Cetie data sheet such as the one for continuous-thread finishes from 43 to 90 mm
Lug	Short interrupted threads; vacuum lug finishes give a vacuum seal on food jars	Cetie lists vacuum lug finishes for wide-mouth containers, plus a fact sheet on glass manufacturing controls for vacuum lug and press-on finishes
Crown	Metal crown crimped over a bead; common for beer	ISO 12821 (26 H 180) and ISO 12822 (26 H 126), with Cetie data sheets; Cetie Guide No. 4 covers 26 mm crown capping
Cork	Stopper seals inside the bore	A cork mouth finish under EN 12726 (18.5 mm bore) for still wines, per Cetie Guide No. 1
ROPP (roll-on pilfer-proof)	Aluminum shell is rolled onto the finish to form thread and tamper band	Cetie lists these finishes by names such as BVP, BVS and MCA, each tied to a standard, such as EN 15543 for BVP and EN 16293 for deep BVS finishes

Cetie notes that closures are often delivered in an intermediate state, so the bottle finish acts as the template for the final closure shape. Cetie also says the finish standards for the major systems are applied by all glass makers, with each cap maker tailoring closures to them.

Why nominal diameter alone is not enough

Several checks go beyond the diameter number.

• Thread style. Propacks notes that a 24-410 cap may thread onto a 24-400 bottle far enough to feel secure, but the thread geometry is different and the seal cannot be assumed.
• Different standards, same diameter. A GPI continuous-thread finish and a European ROPP-type screw finish can be close in nominal size yet belong to different standard families (Cetie’s finish list includes a 28 mm screw finish tied to its MCA series). Confirm the finish name, not just the millimeter size.
• Sealing surface. Cetie describes closures that seal inside the neck, on the top lip, or on a mixed area including part of the inside or outside. The finish must provide the surface the closure is built to seal on.
• Additional components. The Cary Company notes that liners, sifter fitments, dip tubes, plug seals and shrink bands can change how a closure sits or engage the thread.
• Maker variation. The same guide adds that manufacturers’ designs and materials vary, and that some child-resistant caps have shorter threads and narrower fit tolerances.
• Application conditions. Fill temperature, pressure and the capping process all affect fit, according to the same guide.

How closure compatibility is verified

Verification combines documents, samples and tests on the actual line, and no single step is enough.

Step	What it checks	Notes
Drawing and standard review	Finish designation, T/E/I/H/S, sealing surface, tolerances	Ask both the bottle and closure supplier to confirm the same finish
Liner review	Liner type against product, temperature and seal type	Liner changes the torque window, per Propacks
Sample fit	Thread engagement, orientation, seating	Cary recommends requesting a sample of each and testing the fit
Torque study	Application and removal torque	See below
Seal and leak tests	Leak, vacuum, pressure or pull-up checks suited to the closure	For vacuum lug closures, Cetie assigns fill level and vacuum responsibility to the filler and cap supplier
Line trial	Behavior at the actual capping speed, fill temperature and product	Treat any change in closure, liner, finish or product as a changed package

Torque and liners

Application torque is the force used to put the closure on. Removal torque is the force to open it after settling. Propacks states they are related but not interchangeable, and that a capper dial or recipe is a process input, not a verified torque result. A distributor guide from eBottles adds that a capping machine’s applied torque cannot be measured directly, so the removal torque of machine-capped closures is measured and correlated.

Propacks cites many packaging programs using a 24-hour hold because closures relax, and a common reference of removal torque at roughly 40% to 60% of application torque, which it calls a screening guideline, not an acceptance range. It also states that closure diameter helps set a starting point but cannot set a final torque specification, because resin, thread profile, liner, tamper band and bottle material change the result. Published torque tables are screening values. The approved range has to come from tests with the exact bottle, closure, liner and product.

Standards and guides to cite

Cetie publishes bottling guides for specific closures, including crown capping, metallic screw capping on BVP and BVS finishes, and a guide to ROPP defects. Cetie Guide No. 9 states that for pressurized products both cap and bottle must be foreseen for the application, subject to a written agreement among the cap supplier, bottle supplier and filler. Propacks refers to ASTM D2063 (torque retention), ASTM D3474 (torque meter calibration) and ASTM D7860 (automated torque testing) for continuous-thread packages. Ask which of these the supplier uses.

Questions to send suppliers

1. What is the exact finish designation or standard of this bottle, and can you send the drawing with T, E, I, H and S and tolerances?
2. Which closure and liner do you recommend for this finish, and which finish drawing does the closure maker use?
3. What sealing surface does the closure rely on, and what controls on planarity or finish quality apply?
4. Do you hold application and removal torque data for this combination, and under what conditions (liner, product, temperature, hold time)?
5. What fill temperature, pressure or vacuum condition has this bottle-closure pair been validated for?
6. Can you provide samples of the bottle and closure for a fit and line trial?
7. What happens to the validation if the liner, closure maker or product changes?

Closure application is covered in capping equipment for glass bottles and jars. For a list of data to send with these questions, use the bottle specification checklist. Shape and sourcing context is in glass bottle types and sourcing. Application-specific closure choices are discussed in wine bottling equipment and beer bottling equipment. When a new bottle joins an existing line, see bottling-line changeovers.

Evidence and limitations

The T, E, I, H and S definitions and GPI conventions here come from distributors’ explanatory guides, not from GPI’s own drawings, which were not available for review. European finish and closure information comes from Cetie’s public data-sheet listings, whose full documents require a free account. Torque ranges are screening values from a supplier guide. This guide cannot confirm that a given bottle and closure are compatible. That depends on the finish drawing, closure design, liner, product, line and supplier, and it must be confirmed by testing.

• Guide to Neck Finishes, The Cary Company: T, E, I, H and S definitions, designation format, and additional fit factors (distributor guide).
• Guide to Bottle Neck Finishes, Thread Sizes, & Dimensions, Paramount Global: GPI/SPI thread styles (400, 410, 415) and dimension definitions (distributor guide).
• Closure Torque Guide: Application, Removal, and Testing, Propacks: torque concepts, hold-period testing and the limits of torque tables (supplier guide).
• Application and Removal Torque Guidelines, eBottles: the removal torque method for verifying machine-applied closures (supplier guide).
• Cetie finish data sheets (GME), Cetie: crown, lug, continuous-thread, BVP and BVS finish specifications.
• Cetie bottling guides, Cetie: guides for cork, ROPP, crown and screw capping and written agreement for pressurized products.
• Cetie also gives guidance for metal caps, Cetie: how closures and finishes are defined together, sealing areas and finish standards.
• Cetie recommendation data sheets (FS), Cetie: fact sheets on vacuum lug manufacturing controls and headspace responsibility.