Inside the reusable pen: how each click meters a volume
6 min read · Updated September 2026 · MY PEPTIDES Research Team
Key facts
The reusable pen is a precision volumetric dispensing device built around a 3 mL cartridge. Twist the dose knob and a threaded push-rod turns with it, translating that rotation into straight-line travel that pushes a plunger forward and drives solution out of the cartridge; a tactile click ratchet marks off one audible, feelable click per increment, so every click is a discrete, repeatable step instead of a free-running slide. In mechanical terms, one click equals 1/300th of a full plunger advance. With a 3.0 mL cartridge and a fixed 0.01 mL per click, that works out to 300 clicks per cartridge (3.0 mL divided by 0.01 mL). Holding that step constant is what keeps volumes repeatable across a study. Before any measuring begins, a handful of priming clicks clears air out of the cartridge and needle path so the clicks that follow push liquid rather than air. The cartridge can be loaded from a reconstituted powder or from one of our pre-mixed US vials, which arrive as a solution at a known concentration and skip reconstitution entirely. The device is for in-vitro laboratory research use only: it meters a volume, not a dose, is not for human or veterinary use, and the research compounds a cartridge may hold have not been evaluated by the FDA.
The reusable pen is a precision volumetric dispensing device built for a 3 mL cartridge. What follows explains how the mechanism meters steady, repeatable volumes, strictly as device documentation. The figures below (a 3 mL cartridge, 0.01 mL per click, 300 clicks) describe the hardware and do not change.
Research use only, and a dispensing device rather than dosing guidance. This covers the mechanics of measuring and dispensing volumes of reconstituted or pre-mixed solutions for in-vitro laboratory research. It is not guidance on human or veterinary use, it does not cover administration technique, it holds no dosing protocols, and the research compounds a cartridge may contain have not been evaluated by the FDA. Researchers decide the volumes their own experiments call for.
What is inside
- Dose knob. Turned to set the increment.
- Tactile click ratchet. Gives an audible and feelable click per increment.
- Threaded push-rod. Turns knob rotation into linear travel.
- Plunger. Pushed forward by the push-rod to displace solution from the cartridge.
- 3 mL cartridge. Holds the reconstituted or pre-mixed research solution.
- Needle hub and needle. The dispensing tip.
What one click does
Turn the dose knob and the threaded push-rod rotates, advancing the plunger by a fixed, precise amount. The ratchet fires one tactile click per increment, so each click is a discrete, repeatable step rather than a free-running slide. Mechanically, one click equals 1/300th of a full plunger advance. You feel and hear the step, which is what lets you count volume without watching a scale.
The volume behind each click
The math falls straight out of the cartridge size and the increment:
- Full cartridge volume: 3.0 mL
- One click: 0.01 mL
- Total clicks per cartridge: 3.0 mL divided by 0.01 mL = 300 clicks
That fixed 0.01 mL step is the entire point of the device: it lets you put out the same small volume every time, which is what makes measurements repeatable across a study. Because the step is mechanical rather than eyeballed, two people running the same protocol on the same cartridge dispense the same volume.
Loading a cartridge
The cartridge holds whatever solution the work calls for. If you are working from lyophilized powder, you reconstitute it first (see how to reconstitute peptides) and load the resulting solution. If you are working from one of our pre-mixed US vials, the solution is already at a known concentration, so the cartridge is filled from a ready solution with no reconstitution step in between. Either way the pen meters a volume; the concentration of that volume is set by the solution, not by the pen.
Priming first
Before you measure anything, a set of initial priming clicks expels air from the cartridge and needle path, so the clicks that follow dispense liquid instead of air. It is a one-off mechanical prep step, separate from measuring a volume, and skipping it is the most common reason an early measurement reads short.
Why the precision earns its keep
In a research workflow, repeatability is everything. A device that hands you the same 0.01 mL per click removes a source of variability, so a result can be tied to the compound rather than to uneven handling. Start from a verified material with a batch-specific Certificate of Analysis, store solutions correctly (storage guide), and match the solvent to the compound (bacteriostatic water and stability).
How the pen and our vials ship in the US
The Reusable Auto-Injector Pen and its needles ship to US laboratories with the rest of an order. The research solutions the pen dispenses are synthesized in our own UK laboratory and verified in a US laboratory before each US batch is released, then supplied pre-mixed with a batch-specific Certificate of Analysis (HPLC for purity, mass spectrometry for identity). Orders are dispatched cold-chain from the warehouse serving the United States, with tracked delivery next business day, priced in US dollars and payable by Visa, Mastercard or Apple Pay. Store the solution vials refrigerated at 2-8°C on arrival; the pen itself is hardware and needs no refrigeration.
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Reusable Auto-Injector Pen
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Frequently asked questions
- How many clicks does a 3 mL cartridge hold?
- At a fixed 0.01 mL per click, a 3 mL cartridge works out to 300 clicks (3.0 mL divided by 0.01 mL). This is device mechanics: it describes a volume, not a dose.
- What volume does a single click deliver?
- One click moves the plunger a fixed 0.01 mL, which is 1/300th of a full 3 mL cartridge. That steady increment is what makes volumetric dispensing repeatable.
- What does priming the pen do?
- It runs a one-off set of initial clicks that push air out of the cartridge and needle path, so later clicks dispense liquid rather than air. It is a mechanical prep step, not part of measuring a volume.
- Does the pen work with your pre-mixed US vials?
- Yes. The cartridge is filled from whatever solution you are using. Our US vials arrive pre-mixed at a known concentration, so you load a ready solution with no reconstitution step. The pen meters the volume; the solution sets the concentration.
- How quickly does the pen ship in the US?
- The pen and needles ship with the rest of a US order, dispatched from the warehouse serving the United States with tracked delivery next business day, priced in US dollars and payable by Visa, Mastercard or Apple Pay. The pen is hardware and needs no refrigeration.