Compare · 3 min read
Pen or vial?
The honest trade-offs, and who each one suits.
Several peptides come in two formats: a traditional vial you mix yourself, or the Stack One pen — a pre-filled, pre-mixed cartridge you dial.
| Stack One pen | Vial | |
|---|---|---|
| Mixing | None — pre-mixed | You add BAC water |
| Measuring | Turn a dial | Draw units on a syringe |
| Flexibility | Fixed steps (with clicks in between) | Any dose you can measure |
| Learning curve | Lowest | A little practice |
| Kit | Pen needles | Insulin syringes, swabs, BAC water |
How the pen dial works
The dial runs from 1 to 5, and each number delivers a fixed slice of the cartridge. It also clicks between numbers, so you are not limited to whole steps — useful for starting gently. Each peptide page’s dossier tells you whether a pen exists; Ask for the exact dial for your cartridge.
Who suits which?
- New to all this? The pen removes the two steps people find most intimidating — mixing and measuring.
- Want fine control? Vials let you set any dose and adjust the dilution.