Find the bottle's complete specification
When choosing a pump for soap dispenser bottles, identify the connection before looking at the color. The featured PEHADU black set is specified by its seller for standard 28/400 threaded bottle necks. That complete designation matters. A bottle described only as having a 28 mm opening has not yet been shown to have the same finish.
Look for the neck-finish specification in the bottle maker's documentation or ask the bottle supplier. Bottle capacity, glass or plastic construction, and brand name do not identify the threads. If the bottle has no reliable specification, record that as an unresolved fit question. A photograph can help a supplier discuss the part, but it cannot establish all dimensions and tolerances.
Why a rough diameter cannot settle it
The seller gives an approximate outside neck diameter of 26–28 mm. Treat that as a reference alongside the stated 28/400 finish, not a promise that every neck within the range will fit. Berlin Packaging's neck-finish guide distinguishes thread outside diameter, neck outside diameter, finish height and other measurements. Together these explain why a single ruler reading leaves important details unknown.
The packaging guide is general background, not a compatibility test of this pump. We have not obtained an engineering drawing or tolerance data for the featured part. A different suffix, incomplete neck specification or uncertain measuring point should prompt a question to the bottle or pump supplier rather than a claim of interchangeability.
Use a fit checklist before replacing the top
A soap dispenser top replacement is a connection decision as well as a cosmetic one. First confirm the finish, then inspect the bottle's existing neck for visible damage. If a candidate closure does not start squarely or feels cross-threaded, stop rather than forcing it. A fit problem at the connection cannot be fixed by cutting a shorter dip tube.
Keep a separate note of tube reach and room for the spout. The seller graphic labels a 5.5 cm (2.16 in) head-and-spout span; that is not the cap diameter. The graphic's 9.2 cm (3.62 in) pump assembly height includes a lower connecting section and is not the amount that will stand above your bottle. Those distinctions matter beside a backsplash or under a shelf.
| What you know | What it supports | What remains open |
|---|---|---|
| Bottle documented as 28/400 | Matches the seller's named finish | Actual fit, condition and installation |
| Rough outside diameter only | An initial size reference | Thread geometry and complete finish |
| Bottle capacity or material | A description of the container | Neck compatibility |
| Head-and-spout span in graphic | A seller-reported horizontal dimension | Exact installed clearances |
Make the decision explicit
For example, two bottles can both be sold as 12-ounce dispensers while using different closures. Capacity alone gives neither one an advantage in this fit check. Choose on documented connection details and measured installation needs. If the bottle's finish remains unknown, ask for that detail before ordering; do not treat a similar cap as proof.
Once the neck has been checked, move to tube measurement. If the old dispenser is not pumping, remember that a replacement head is not a diagnosis: bottle fit, tube position and the liquid can each affect the outcome. This guide offers a selection process, not a guarantee that a new pump will resolve every dispensing problem.