Almost every packaging problem we are asked to fix starts with a measurement that was taken from the wrong part of the vial. It is an easy mistake, it costs a set of insert tooling, and it takes about five minutes to avoid.
What you need
A digital calliper is ideal and inexpensive. A steel rule will get you close enough to start a conversation, but not close enough to cut tooling from. If you have neither, skip to the last section — posting us a vial is genuinely the better option.
Take measurements from more than one vial. Glass varies within a batch and varies more between batches, and a cavity tuned to a single sample can be uncomfortably tight for the next one.
The four measurements
1. Body diameter
Measure across the widest part of the straight glass body, ignoring the shoulder and the base. This is the number a foam cavity is cut against, because foam grips the body directly.
Take it in two places at ninety degrees to each other. Moulded vials in particular are not perfectly round, and the difference between the two readings tells us how much variation the cavity has to tolerate.
2. Cap diameter
Measure across the widest point of the closure — usually the flip cap or the crimp skirt, not the glass. This is almost always the widest part of the whole vial, and it is the number that sets the opening on a die-cut paperboard insert, because the vial has to pass cap-first through the hole during loading.
This is the measurement people skip, and it is the one that stops a carton working. A hole sized to the body diameter will not accept the cap at all.
3. Total height over the cap
From the base of the vial to the highest point of the closure. Not to the top of the glass, and not to the shoulder — to the top of whatever is fitted.
Internal box height is derived from this plus clearance, so that the lid or the top flap never rests on the crimp seal. Getting it wrong produces a box that will not close flat, or one that presses on the closure every time it is stacked.
4. Shoulder height
The distance from the base to the point where the straight body starts curving inward. This tells us how deep a cavity can be before it stops gripping useful glass, and it is what determines whether a raised paperboard platform will hold the vial at its body or slip up to its neck.
It is also the number that sets the usable height of a vial label, since a label that runs onto the shoulder curve will lift at the edges.
The mistake almost everyone makes
Measuring the body and assuming the cap is the same or smaller.
On most peptide vials the flip cap overhangs the glass by a millimetre or more on each side. An insert cut to the body measurement will not accept the vial at all, and the first anyone knows about it is when the tooling has been made and a sample arrives that will not load.
If you take only one measurement from this article, take the cap.
What else to tell us
Numbers alone do not describe everything that affects the fit.
- Whether the vial is moulded or tubing glass. Moulded vials have thicker walls and more dimensional variation; tubing vials are more consistent and slightly narrower for the same nominal volume.
- The closure type. A flip cap, a plain crimp seal and a screw cap behave differently in a cavity.
- Whether the vial is filled at the point of packing. A filled vial is heavier, which changes insert and board specification.
- Whether loading is by hand or by machine. This changes cavity chamfer and fit tolerance more than the dimensions do.
- Anything else in the box. A syringe, an ampoule, a leaflet — each needs its own profile, and adding one later usually means redesigning the insert.
Why sending a vial is better
We will always work from measurements if that is what you have, but a physical sample removes several things that are difficult to communicate on paper: shoulder profile, closure overhang, glass finish, and how the vial actually behaves when it is pushed into a cavity.
Postage costs a few dollars. A set of insert tooling cut to the wrong dimension costs considerably more, and the delay costs more again. Send two or three vials from the batch you will actually be running, and we will design the cavity around the real range rather than a single sample.
Once you have the numbers
Send them with two further pieces of information — how many vials go in a box, and whether that box ships on its own or inside an outer case — and that is enough for a full specification. Everything else, from board caliper to insert type, follows from those inputs. The how to order page sets out what happens next.
Further reading
How to Choose Boxes for 2ml, 3ml, 5ml and 10ml Vials
Between 2ml and 10ml a vial roughly triples in filled mass. That single fact drives almost every difference in how the four sizes are packaged.
Common Mistakes to Avoid When Ordering Custom Vial Boxes
Most expensive packaging mistakes are made in the first week of a project, before anything is printed.