When you ask a spout cap supplier for specifications, you usually get a catalog page: a photo, a diameter, a material code and a list of applications. That page is a start, but it is not a specification. A usable specification sheet for a stand-up pouch or doypack answers two questions first: what is the spout inner diameter, and what is it made of — PE or PP? Thread style, cap type, sealing behavior and certifications all hang off those two answers.
This guide is written for pouch converters, packaging engineers and brand buyers who are reading — or writing — a spout cap spec sheet. It covers the two numbers that decide whether a fitment works for your product, the tolerances worth checking, and the material decision most catalogs leave you to figure out alone. Everything here is about spout caps for stand-up pouches and doypacks: the resealable plastic fitments heat-sealed into flexible beverage, sauce, cosmetic and liquid-food pouches. If you are looking for a gas-can spout cap or a bottle pour spout, this is not the reference you want. It is part of our choosing and running spout caps series for buyers and converters.
Reading spout cap specifications: start with inner diameter and material
A typical datasheet for a pouch spout lists a dozen parameters: inner diameter, cap and spout dimensions, height, weight, material grade, color, sealing temperature, and compliance marks. Each of those matters to someone, but two of them are load-bearing. Get them right and the rest of the sheet is detail. Get them wrong and no amount of thread polish saves you: the spout either pours too fast or drips, or it welds into your film with a weak seal, or it fails food-contact review in your target market.
The other reason to fix these two first is that pouch spouts live in a different spec world than bottle caps. Bottle closures are described by neck finishes — 28-400, 24-410 and similar codes that define the finish on the container. A pouch spout has no neck finish: it is heat-sealed into the film, so the dimensions that matter are the bore the product flows through, the flange that welds into the pouch, and the cap that reseals it. If a supplier's "specifications" only quote a bottle-style finish, they are not describing a pouch fitment at all.
Spout inner diameter: where it is measured and why it matters
The spout inner diameter is the bore of the spout — the opening the product passes through when the cap is open. It is measured with a caliper across the inside of the bore, at the point where flow is constrained. On a datasheet it is the number next to "inner diameter" or "I.D.", and it is almost always expressed in millimeters for pouch fitments.
The inner diameter is the bore of the spout, measured across the opening with a caliper.
Two details are worth checking on any spec sheet before you compare suppliers:
- The tolerance. A stated "8.6 mm" means nothing without a tolerance. A ±0.1 mm working tolerance on spout inner diameter is a reasonable benchmark to require in an RFQ — it tells you how consistently the fitment will mate with your filling and capping equipment across a production run.
- Where it is measured. Inner diameter can be quoted at the tip, at the seat, or averaged along the bore. Two sheets that both say "10 mm" may describe different openings. Ask which point the number refers to if the drawing does not make it clear.
Why does it matter? Diameter controls flow rate and dosing behavior. A narrow bore doses slowly — right for essential oils and serums, wrong for a refill pouch that has to empty fast. It also interacts with the cap: the spout bore and the cap's internal geometry are designed as a pair, so changing one without the other invites leaks or hard-to-open caps. For a fuller decision framework on matching bore to product and line, see how to match spout diameter to your product and line.
Common spout inner diameters for stand-up pouches
Most pouch spouts fall into a small set of well-trodden bores. The table below shows the sizes that recur across food, beverage, daily-chemical and cosmetic pouches, with the applications each one typically serves.
Spout inner diameter | Typical applications |
|---|---|
1.2 – 3.5 mm | Cosmetic essences, cleansing oils, serum sachets — precise, small-dose dispensing |
5 – 6 mm | Travel-size shampoo, body wash and hand-sanitizer sachets |
7 mm | Lip gloss, eyeliner, mascara and other thin-tube cosmetic pouches |
8.6 mm | The workhorse bore: juice, sauce, jelly, ketchup, baby food and condiment pouches |
9.6 – 10 mm | Sugar, salt, drinks, liquid detergent and medium-flow jelly pouches |
12 – 14 mm | Non-spill beverage pouches, honey, baby food, pharmaceutical liquids |
16 mm | Baking syrup, honey, jam and other slow-pouring, higher-viscosity products |
21.5 – 22 mm | Sport water bags, laundry detergent refills, tomato paste, high-flow liquids |
30 – 33 mm | Rice, grains, pet food and large-capacity household products |
40 mm | 3–20 kg bulk refill pouches for edible oil, honey and industrial liquids |
The 8.6 mm bore deserves its reputation as the default: it pours liquids cleanly, doses sauces and jellies controllably, and it is the size around which the largest number of cap styles — screw caps, flip tops, anti-choking mushroom caps — have been developed. Ruihua's catalog carries 19 SKUs at 8.6 mm and spans the full 1.2 mm to 40 mm range across 117 spout cap models, all in food-grade PE or PP.
The same product family across different bores: from slim cosmetic fitments to 40 mm bulk-refill spouts, the inner diameter is the first spec that separates them.
Spout cap material: PE vs PP
Once the bore is fixed, the material decision comes next: PE or PP. Both are food-contact plastics with decades of packaging history, and both appear in pouch spout catalogs. They are not interchangeable.
Property | PE (polyethylene) | PP (polypropylene) |
|---|---|---|
Feel and rigidity | Softer, more flexible | Stiffer, firmer thread hold |
Heat resistance | Lower; typical service well below 121 °C | Higher; retort-compatible up to ~121 °C |
Sealing into film | Seals at lower temperatures (110–130 °C) | Needs higher sealing temperatures |
Recyclable-pouch compatibility | Natural fit with mono-material PE films | Works with multi-layer films; separate stream |
Typical fit | Squeeze-and-dose, refill, daily chemical | Hot-fill, sterilized, high-clarity food products |
The decision rule is short: match the spout material to your film and your fill process. If your pouch film is a mono-material PE structure designed for recyclability, a PE spout — or a low-temperature-sealing grade — keeps the whole pack on one polymer family. If your product is hot-filled or retorted, PP's higher heat resistance is the safer choice. Polyethylene's general properties are well documented (see polyethylene on Wikipedia for density and heat-behavior reference); the same holds for polypropylene. The key is that the datasheet's material line is a specification, not a default — and it should be chosen, not inherited from the supplier's stock item.
PE spouts feel softer and seal at lower temperatures; PP spouts hold threads more firmly and take hotter fills. The datasheet's material line should be a choice, not a stock default.
This is also where mono-material and recycling goals enter the conversation. For a deeper look at how spout material interacts with recyclable pouch structures, see our guide to mono-material recyclable PE pouches.
Material and sealing temperature work together
Inner diameter and material are static numbers; sealing temperature is where they meet your production line. The spout is welded into the pouch film on a spout sealing station, and the material pair — spout polymer and film sealant layer — must melt and bond in the same window.
Low-temperature sealing is the reason PE spouts are so common in flexible packaging. A PE spout engineered to weld at 110–130 °C protects thin films from scorching and allows faster line speeds. A PP spout, with its higher melt temperature, demands a hotter sealing zone and more careful control. If the sheet quotes a sealing range at all, it is the single most useful number on the page for a converter — and one of the most frequently omitted. For the full picture on seal temperatures, dwell time and film compatibility, read our guide to spout sealing temperature.
Food-contact compliance: what the certifications actually tell you
A spec sheet for food packaging is only half useful if the compliance line is vague. Three marks cover the majority of export markets:
- US FDA — food-contact compliance for materials in contact with food. The FDA regulates food contact substances rather than "certifying" individual products, so a supplier's FDA documentation is a material-compliance statement. The FDA's food ingredients and packaging program is the authoritative reference.
- EU 1935/2004 — the framework regulation for all food-contact materials in the EU, setting the safety baseline; the plastics-specific rules sit in Regulation (EU) 10/2011. Both are the instruments a buyer should name when asking a supplier "are your spouts compliant for Europe?" — see (EC) No 1935/2004 on EUR-Lex and (EU) No 10/2011 on EUR-Lex.
- ISO 9001 — not a food-safety mark, but the quality-management system that gives the other claims a process to stand on (ISO 9001:2015 overview).
What should a buyer do with this? Ask for the certificate, check the scope line, and confirm it covers your destination market — US, EU, or both. At Ruihua, spout caps are produced under ISO 9001:2015, HACCP and EU 1935/2004 (TUV SUD) certification with US FDA food-grade material compliance, and individual products additionally reference GB 4806.7 and EU LFGB. The practical implications of each certificate for a pouch project are unpacked in food-grade spout cap certifications.
Certificates only mean something if the process behind them is real — which is why the quality system and inspection practice matter as much as the paper.
A five-point checklist before you order
Before you send a spout cap requirement to any supplier, make sure the sheet answers these five points:
- Inner diameter and tolerance — the bore in millimeters, and the ± tolerance you can expect across production runs.
- Material, chosen not inherited — PE or PP, and why it matches your film and fill profile.
- Sealing temperature range — does the spout weld in the same window as your film's sealant layer?
- Food-contact compliance for your market — certificates and scope covering your destination region.
- Color and cap style — the closure type (screw, flip-top, anti-choking, tamper-evident) and whether the color is stock or custom.
That checklist doubles as an RFQ skeleton. If you are still early in the process, our step-by-step guide to choosing a spout cap walks the full decision order from product to line.
When you need more than a standard spec
Standard bores and stock materials cover most projects, but pouch programs drift off the catalog for three reasons: color, cap style, and a bore that sits between the usual sizes.
- Color. The default for pouch spouts is white. Colored spouts are made to order against a Pantone reference, not pulled from a rainbow of stock — worth knowing before you design a pack around a specific shade.
- Cap style. Anti-choking mushroom caps for baby food, flip-tops for travel sizes, tamper-evident screw caps for retail — the cap is a spec of its own that changes the sheet.
- Custom bore and mold. If you need a dimension or geometry no catalog covers, a custom mold is the path: the quote follows the 3D drawing (mold cost cannot be estimated from a sketch), samples can be 3D-printed from the drawing first, and mold production typically runs about 60 days. Custom mold projects have no minimum order quantity — the mold commits the supplier to you.
For the full picture on custom tooling lead times and mold costs, our custom spout cap service page explains how a custom project moves from drawing to mass production.
Get a spout cap spec sheet matched to your pouch
You should not have to reverse-engineer a catalog to write your own specification. Tell us your product, your pouch film structure, and your line's sealing temperature, and Ruihua will point you to the spout cap specifications that fit — bore, material and cap style, with the compliance documentation you need for your market. Start from the plastic spout cap product range or send your parameters through the contact page, and we will reply with a spec sheet instead of a sales pitch.
