Fit is a set of geometry statements
Fit is the relationship between the band and the body, and it is described by geometry rather than by feel. The parts that decide fit are the band length range, the closure position, the inner curve of the band, the contact area, the clearance between the mechanism and the surface, and the skin-contact material. Each of these is a measurable property of the shell and the band, and each can be quoted on a sample. This glossary defines the terms in neutral language and separates them from the terms a buyer might confuse them with.
See neck-massager-fit-pressure-distribution for the verification method behind these terms, and neck-massager-office-seated-work-fit for how fit is read in a desk setting.
Glossary table: fit and contact terms
| Term | Neutral definition | What it is not |
|---|---|---|
| Fit | The relationship between the band geometry and the body shape | A body outcome |
| Pressure distribution | How the contact load is spread across the contact area | A measured value without a method |
| Contact area | The surface area of the skin-contact part that meets the body | The pressure applied |
| Band length range | The range of neck sizes the band can close over | The contact area |
| Closure position | Where the band closes relative to the mechanism | The band length |
| Inner curve | The shape of the band on the side that faces the body | The contact material |
| Clearance | The space between the mechanism and the body-facing surface | The contact area |
| Contact load | The force the band places on the contact area | The pressure distribution itself |
| Band rigidity | How much the band resists bending | The shell rigidity |
| Skin-contact surface | The silicone over-mould, fabric pad or gel pad that meets the skin | The band geometry |
| Shell geometry | The shape of the outer plastic part | The band length range |
| Golden sample fit | The fit measured on the approved sample | A production guarantee |
| Fit tolerance | The acceptable variation in band length and closure position | A pressure figure |
| Noise fit | Whether the mechanism tone fits the intended space | The fit geometry |
The contact area entry
The contact area is the surface area of the skin-contact part that meets the body. It is a geometry figure, measured from the pad or the over-mould, and it is not the pressure applied across it. A wider contact area spreads the same contact load over more surface, and a narrower contact area concentrates it. The contact area is set by the shell and the pad, and it can be measured on a sample.
The contact area is not the pressure distribution. Two units can have the same contact area and different pressure distributions, because the distribution depends on the shape of the pad, the band rigidity and the closure position. A buyer who asks for a contact area figure and receives a statement about comfort has received an answer about a different property.
The pressure distribution entry
Pressure distribution describes how the contact load is spread across the contact area. It is a property of the geometry and the material, and it can be checked by measuring the contact load and the contact area together. A distribution that is even across the contact area and a distribution that is concentrated at the edges are two different properties, and the difference comes from the pad shape, the shell rigidity and the band rigidity.
A pressure distribution figure without a method is not a measurement. Ask which method produced the figure, whether the figure was taken on a sample or on a production unit, and whether the figure is reported as a range or as a single value. See neck-massager-fit-pressure-distribution for the verification method.
The band length range and the closure position
The band length range is the range of neck sizes the band can close over, and the closure position is where the band closes relative to the mechanism. The two are different properties. A band with a wide length range and a closure that sits far from the mechanism can be awkward to close, and a band with a narrow range and a closure that sits close to the mechanism can be easy to close but limited in size.
The closure position is also where the controller is usually placed, and a closure that sits at the front can press the controller against the body. Ask where the closure sits, whether the controller is on the closure, and whether the closure has a smooth surface.
A boundary to keep in view: contact area is not pressure
Contact area is not pressure, and pressure is not a body outcome. Contact area is a geometry figure, and pressure is the contact load spread across that area. A buyer who asks for a pressure figure and receives a contact area figure has not learned the pressure. Ask for both figures, and ask which method produced each.
The second boundary is that a comfortable fit is not a measured fit. A sentence about comfort describes the wearing experience, and a measured fit describes the band length range, the closure position and the contact area. A buyer who wants a repeatable fit should ask for the measured figures and the tolerance, not for a description of comfort.
Questions to ask a supplier
- What is the band length range, and where does the closure sit relative to the mechanism?
- What is the contact area, and which method was used to measure it?
- What is the pressure distribution figure, and which method and sample produced it?
- Which skin-contact material is fitted, and what is its shore range?
- What is the fit tolerance, and how is it checked on a production batch?
Reading fit from a specification sheet
A fit specification should carry the band length range, the closure position, the contact area, the material and the tolerance. A specification that names the material but not the band length range is not a fit specification. A specification that names the contact area but not the method is not a comparison basis.
The buyer should compare fit across candidates on the same basis: the same posture, the same band length range and the same method. A figure measured on a sample in a standing posture is not the same as a figure measured in a seated posture, because the neck shape changes with the posture. Ask which posture the figure was measured at.
Frequently asked questions
Is a wider contact area always better? Not automatically. A wider contact area spreads the contact load, but it also changes the band width and the shell size. Compare the contact area with the band length range and the shell geometry.
Can fit be verified on a sample? Yes. A golden sample can be measured for band length range, closure position and contact area, and the figures can be recorded against the sample revision.
Next step
Send the fit glossary table to the factory, ask for the band length range, closure position and contact area on a golden sample, and request a tailored quotation through contact. For the verification method, see neck-massager-fit-pressure-distribution. For the material behind the contact surface, see neck-massager-skin-contact-material.
From the Serenivo comfort-product notes. Descriptive material only; no health or medical outcome is stated or implied.