Every cosmetic packaging procurement professional has faced this moment. The design team sends a beautiful bottle rendering. The formula team confirms the product. The marketing team approves the brand positioning. Then someone asks the question nobody thought about: what neck finish does this bottle use, and does the cap fit?
The answer, usually buried in a supplier’s technical drawing somewhere between “thread pitch” and “H dimension,” determines whether your product ships on time or spends six weeks in rework. This bottle neck finish guide explains the two most common neck finishes in cosmetic packaging, 24/410 and 28/410, so you can make the right call before a mismatch becomes a crisis.
The neck finish is not just a technical specification. It is a procurement decision point. Specify the wrong one and your entire closure inventory, caps, pumps, sprayers, may be incompatible with your bottle. The cost of reworking a 50,000-unit order for a neck finish mismatch typically exceeds $15,000.
Neck Finish Basics: What the Numbers Mean
Decoding the GPI/SPI Designation
The standard neck finish designation system used in global cosmetic packaging follows the Glass Packaging Institute (GPI) and Society of the Plastics Industry (SPI) naming convention: Thread Diameter (mm) + Thread Profile + Number of Thread Turns.
Breaking down 24/410:
- 24 = nominal thread outer diameter of 24mm
- 410 = 4 indicates a “400-series” thread profile (the most common for continuous-thread closures); 10 indicates 1.0 thread turns (roughly one full rotation)
Breaking down 28/410:
- 28 = nominal thread outer diameter of 28mm
- 410 = same 400-series profile with 1.0 thread turns
The thread profile number (400-series vs 415-series vs 425-series) defines the thread’s cross-sectional shape, crest and root radii, and pitch. The 410 is the workhorse of cosmetic packaging. Roughly 80% of all cosmetic continuous-thread closures use this profile. If you are specifying a neck finish for the first time and have no reason to deviate, 410 is the safe default.
Why 4mm Matters
The 4mm diameter difference between 24/410 and 28/410 may sound trivial. It is not. That 4mm represents a 17% increase in thread circumference (75.4mm to 88.0mm), which changes the total thread engagement area. It also represents a 36% increase in neck cross-sectional area (452mm² to 616mm²), which affects fill speed, air displacement during capping, and visual proportions. And it creates a fundamentally different consumer hand-feel: 24/410 necks feel proportionate on 30ml to 150ml bottles, while 28/410 necks visually match 200ml to 500ml bottles.
Detailed Specification Comparison: 24/410 vs 28/410
| Specification | 24/410 | 28/410 | Notes |
|---|---|---|---|
| Thread outer diameter (T dimension) | 24.00mm ±0.20mm | 28.00mm ±0.20mm | Measured at thread crest |
| Thread root diameter (E dimension) | 22.40mm ±0.20mm | 26.40mm ±0.20mm | Measured at thread valley |
| Neck inner diameter (I dimension) | 18.00mm ±0.30mm | 21.00mm ±0.30mm | Critical for pump dip tube clearance |
| Thread pitch | 3.17mm (8 TPI) | 3.17mm (8 TPI) | Same pitch, threads per inch identical |
| Thread turns | 1.0 to 1.5 | 1.0 to 1.5 | Typically 1.0 turn for both |
| H dimension (neck height) | 14.50mm ±0.25mm | 14.50mm ±0.25mm | Measured from top of neck to start of transfer bead |
| Typical bottle volume range | 10ml to 200ml | 100ml to 500ml | Overlap at 100 to 200ml where either works |
| Typical cap outer diameter | 27 to 30mm | 31 to 35mm | Visual proportionality on standard bottle forms |
| Common bottle materials | PET, PP, HDPE, glass | PET, PP, HDPE, glass | Both work across all common materials |
| Compatible closures | Screw caps, disc tops, lotion pumps, fine mist sprayers, treatment pumps | Screw caps, disc tops, lotion pumps, trigger sprayers | 24/410 has broader sprayer compatibility |
| Typical application torque | 8 to 12 in-lb | 10 to 15 in-lb | Higher torque for larger diameter to maintain seal |
| Removal torque after 24h | 6 to 10 in-lb | 8 to 13 in-lb | Consumer opening experience |
| Mold cost (single cavity) | $2,500 to 4,500 | $3,000 to 5,000 | Neck finish tooling only; bottle mold additional |
| Per-unit premium (28/410 vs 24/410) | Baseline | +$0.003 to 0.008 | Marginal on bottles; larger delta on closures |
Common Applications by Neck Finish
24/410: The All-Purpose Standard
The 24/410 neck finish dominates the 15ml to 200ml bottle range in cosmetic packaging. It works for serums and treatments in the 15ml to 50ml range, where the smaller neck diameter visually matches compact premium formats and accommodates both dropper bulbs and airless pump crimp necks. It handles toner and essence bottles from 100ml to 200ml, balancing dispensing control with fill-line efficiency. It is also the neck finish with the widest fine mist sprayer compatibility across manufacturers for 30ml to 150ml mist and spray bottles.
For travel-size products in the 15ml to 50ml range, 24/410 is the only proportionally correct option. It is also the industry-standard pump neck finish for 100ml to 250ml lotion bottles, including our 24/410 plastic lotion pump.
When should you question 24/410? Three scenarios. First, bottle volume exceeds 200ml and the neck looks visually undersized. Second, the product requires high-viscosity dispensing through a wide orifice. Third, your filling line uses large-diameter nozzles above 14mm, which will not fit through an 18mm neck inner diameter.
28/410: The Large-Format Choice
The 28/410 neck finish is standard for 250ml to 500ml bottles. Shampoo and conditioner bottles use it because the larger neck accommodates higher-viscosity product dispensing and faster filling. Body wash and shower gel follow the same logic: fill speed matters at volume, and a 28/410 neck allows a 16mm fill nozzle versus 13mm for 24/410.
Body lotion bottles in the 200ml to 400ml range pair with a lotion pump in 28/410 for full-size body care formats. Large-format hand soap at 300ml to 500ml uses it because consumer expectation demands a substantial-feeling pump on larger bottles.
When sourcing plastic screw caps for PET bottles, the 28/410 neck is standard for 250ml+ PET bottles in global markets. Specifically, plastic screw caps for pet bottle 28mm are a distinct product category. Ensure your cap supplier understands this is a 28/410 cap, not a generic 28mm cap, as the thread profile differs. A generic 28mm cap may have a 415-series or 425-series profile that will not mate with a 410-series bottle neck.
Question 28/410 when bottle volume drops below 100ml (the neck visually dominates the bottle), when the product is a premium serum or treatment (28mm neck reads as mass-market), or when mist sprayer compatibility is required (fewer fine mist sprayer options exist in 28/410).
The 100 to 200ml Overlap Zone: How to Choose
Between 100ml and 200ml, both 24/410 and 28/410 are viable. Here is your decision framework:
| If your product is… | Choose | Reason |
|---|---|---|
| A premium serum ($40+ retail) | 24/410 | Smaller neck signals premium; consumer associates smaller orifices with concentrated formulas |
| A daily body lotion | 28/410 | Larger neck signals volume and value; consumer expects fast dispensing |
| A facial mist or toner | 24/410 | Broader fine mist sprayer availability |
| A body wash or shampoo | 28/410 | Faster filling; standard for this category |
| A refill pouch system | 28/410 | Larger opening for refill pouring; less spillage |
| An airless pump format | 24/410 | Airless pump collar compatibility; visual proportion with smaller bottle formats |
| A hotel amenity bottle (30ml) | 24/410 | Only viable option at this volume, 28/410 neck would appear disproportionate |
Thread Compatibility: The Trap to Avoid
GPI/SPI 400-Series vs Non-Standard Threads
The GPI/SPI system is the global standard, but not universal. Some Asian manufacturers, especially for non-export domestic market products, use proprietary thread profiles that are approximately 24mm or 28mm but do not conform to the 400-series profile. These caps may thread onto your bottle initially but fail under torque testing or develop seal failures after weeks in transit.
When receiving closure samples from a new supplier, perform a four-step thread compatibility test before placing a production order. First, visual inspection: check that the closure’s thread start engages smoothly with the bottle’s thread start, with no cross-threading or forcing. Second, torque test: apply the closure at the specified application torque and measure removal torque after 24 hours. A removal torque more than 30% above specification suggests thread interference. Third, leak test: fill bottles with water, apply closures at spec torque, invert for 24 hours. Any leakage indicates thread mismatch or inadequate liner compression. Fourth, cycle test: open and close 50 times, then measure torque before and after. A torque decay greater than 20% suggests thread wear from profile mismatch.
The “Same Neck, Different Material” Issue
A neck finish dimension is a geometric specification that applies regardless of material. A 24/410 neck on a glass bottle is dimensionally identical to a 24/410 neck on a PET or PP bottle. However, different materials behave differently in production.
Glass necks have tighter tolerances, typically ±0.15mm versus ±0.25mm for plastic, because the molding process is more precise. Closures that seat perfectly on glass may feel loose on plastic bottles from a different mold.
PET bottle necks expand slightly during hot-fill processes. If your product is hot-filled above 60°C, specify the neck dimension at the filling temperature, not at ambient. A neck measured correct at 25°C can be 0.3mm oversized at 85°C fill temperature.
PP bottle necks have higher thermal expansion than PET, which can cause closure loosening in hot environments. For PP bottles shipping to hot climates, specify a slightly tighter thread fit or a higher application torque.
Specifying Neck Finishes in Your Purchase Order
Do not write “24/410 neck” on a purchase order without these three additional specifications.
1. Thread Standard
Specify “GPI/SPI 24/410,” not just “24/410.” The GPI/SPI prefix confirms the screw cap thread specification standard. Without it, a supplier may deliver a proprietary 24mm thread that does not mate correctly with your closures. This happens more often than you would expect, especially with suppliers who serve both export and domestic markets.
2. Material and Process
Example: “GPI/SPI 24/410 neck on PET injection-stretch-blow-molded (ISBM) bottle, ambient-fill process.”
3. Tolerance Class
For cosmetic applications, specify “Standard GPI tolerance” (±0.25mm for plastic, ±0.15mm for glass). For applications requiring tighter closure registration, such as a decorative over-cap that must align with bottle graphics, specify “Tight GPI tolerance” and be prepared for a 10 to 20% mold cost premium.
The most common procurement error in neck finish specification is copying a previous order’s neck finish without verifying that the current bottle’s material and manufacturing process are the same. A 24/410 PET ISBM neck is not functionally identical to a 24/410 PP extrusion-blow-molded neck, even though the GPI dimensions match. Always specify material and process alongside neck dimensions.
Supplier Questions to Ask Before Ordering
Before committing to a neck finish for a new bottle mold, ask your plastic bottle supplier these four questions.
First: do you have existing 24/410 (or 28/410) neck molds on the shelf, or will this require a new neck finish insert? Stock neck inserts reduce mold cost by 15 to 25%.
Second: what is your neck inner diameter tolerance at the specified material and process? This directly affects dip tube clearance for pump and sprayer applications.
Third: can you provide a neck finish cross-section drawing with all GPI dimensions (T, E, I, H, S) clearly marked? Every reputable bottle manufacturer can produce this. If they cannot, find another supplier.
Fourth: what is the neck’s measured shrinkage rate at your target cycle time? Neck dimensions on the CAD drawing are mold dimensions, not final part dimensions. Shrinkage varies by material and process, and a supplier who cannot answer this question has not done their process validation.
Author
Liu Fang — Senior Packaging Engineer with 12 years of experience in rigid packaging component design and manufacturing engineering. Previously led packaging development at a Tier-1 cosmetic packaging manufacturer supplying Estée Lauder, Shiseido, and Amorepacific supply chains. Specialist in injection molding tooling design and neck finish standardization.
Technical Reviewer
Michael Tan — Mechanical Engineer with 18+ years in closure and dispensing system design. Holds multiple patents in tamper-evident closure mechanisms and child-resistant packaging. Former engineering director at a multinational closure manufacturer. Certified in GPI/SPI and ISO 8317 (child-resistant packaging) standards.
Data Source Note
Neck finish dimensional specifications per GPI (Glass Packaging Institute) standards and SPI (Society of the Plastics Industry) 400-series thread profile specifications. Torque specifications referenced from ISO 8317:2015 (child-resistant packaging) and industry best practices across cosmetic closure applications. Mold cost ranges sourced from factory quotations across 8 Chinese mold manufacturers in Yuyao and Guangzhou, Q2 2026. Material shrinkage data based on supplier datasheets and SPE technical papers on polymer processing.