3 mL vs 10 mL vials:
how to tell them apart.
Most vials people keep in the fridge, whether for peptides, insulin, GLP-1 or TRT, are one of two sizes. Here is how to tell them apart in two seconds and store them together.
The two-second check
Look at the metal crimp around the top. A 3 mL vial has a 13 mm crimp. A 10 mL vial has a 20 mm crimp. If the cap is about the width of a pencil eraser, it is 13 mm; if it is closer to a nickel, it is 20 mm.
Side by side
| 3 mL vial | 10 mL vial | |
| Crimp top | 13 mm | 20 mm |
| Body width | ~16.5 mm | ~23 mm |
| Typical height | ~35–40 mm | ~45–50 mm |
| Caps that fit | 13 mm (2–5 mL) | 20 mm (10–30 mL) |
Why the size matters for storage
Most racks are drilled for one size. A 3 mL vial rattles in a 10 mL hole and tips over; a 10 mL vial will not fit a 3 mL hole at all. If you keep both, you either need two racks or a stepped slot that holds both.
Caps and labels by size
Snap-on caps are sized to the crimp, not the vial volume. 13 mm caps fit most 2–5 mL vials, and 20 mm caps fit most 10–30 mL vials. Measure the crimp if you are not sure.
Quick answers
Is a 5 mL vial the same as a 3 mL vial?
Usually the crimp is the same 13 mm, so 13 mm caps fit, but the body can be taller or wider. Check the body width before choosing a rack.
Can one rack hold both sizes?
Yes, if the slots are stepped: a 3 mL vial sits on an inner ledge and a 10 mL vial drops past it. Our Fridge Dock works this way.
Made for this.
Fridge Dock
10 slots. Any slot takes a 3 mL or a 10 mL vial.
Custom Vial Caps · 3 mL
Your label printed on top. 10 snap-on caps per pack.
Custom Vial Caps · 10 mL
Room for 12 letters on the bigger cap.
Signature Kit
Dock + 4 travel pods + 20 caps.