Best Reusable Pens for Research Reconstitution: The Gansulin Metal Pen

A reusable precision click-dial pen (a pen where you turn a dial to choose exactly how much liquid comes out) is one of the most useful tools on a research bench. It turns a reconstituted vial (a small bottle where a powder has been mixed with liquid) into a measured dispenser. You get the same volume every time instead of guessing with a loose syringe. This guide covers what to look for in a reusable research pen, and where the Gansulin metal reusable pen fits in.

Gansulin Metal Reusable Pen

Reusable precision click-dial research pen · standard 3 ml cartridge · 1-60 units

View the pen · $64.99

Why a reusable metal pen for the bench

Disposable plastic pens are sealed and single-use. You throw them away when they are empty. A reusable metal pen works differently. You swap in a fresh 3 ml cartridge (a small glass container that holds 3 milliliters of liquid) when the old one runs out. That makes it the practical choice for ongoing research and demonstration work.

• Repeatable, measured dosing instead of freehand syringe draws.
• Refillable with standard 3 ml cartridges, so supply costs stay low.
• Durable metal body that holds up through repeated bench use.

The Gansulin metal reusable pen

The Gansulin metal reusable pen is a sturdy precision click-dial device built around the standard 3 ml (300-unit) cartridge size (ISO 11608-3, a widely used industry standard). Its main specs:

• Dose range: 1 to 60 units per draw
• Increment: 1-unit steps, with a clear unit counter window
• Cartridge: standard 3 ml / 300-unit glass cartridges
• Needles: standard pen needles (32G x 8 mm), replaced each use
• Body: reusable anodized metal (metal treated to resist scratches and rust)

Key point: the unit counter window and 1-unit clicks are what make a pen useful on the bench. You get the same exact volume every time, which a loose syringe cannot match.

What to look for in a research pen

1. Dose increment. Smaller steps let you draw smaller, more precise volumes.
2. Dose range. A wider range covers more concentrations without re-dialing.
3. Cartridge compatibility. Standard 3 ml cartridges keep refills easy and affordable.
4. Build quality. A metal body and a firm, clicking dial last through repeated use.

The reusable pen options

Reusable cartridge pens are not all the same. They take the same standard 3 ml (300-unit) glass cartridge but differ in build, how you set the dose, and the maximum volume per single draw. The all-metal Gansulin pen is a precision click-dial pen that dials 1 to 60 units in single-unit clicks and delivers liquid with a spring-driven button press (a spring inside pushes the liquid out when you press the button). The V1, V2, and V3 Pens are separate pens, each with its own build and mechanism:

All three V-pens set the dose the same way: pull the end knob out until the marked scale shows your units, then push the knob back in to dispense. Think of it like pulling back a small plunger and pushing it forward. The Gansulin works differently: you dial in the dose, then press a button and a spring inside pushes the liquid out.

Cartridge note: all four pens take the standard 3 ml (300-unit) glass cartridge, but 3 ml cartridges can vary by stopper length (the stopper is the rubber plug at the end of the cartridge). The V1 Pen is built for short-stopper cartridges. Check the stopper type before pairing any pen with cartridges you already own.

The V1, V2, and V3 Pens come in several colors (gold, blue, green, grey and more). Every pen fits the same 3 ml cartridges, so refills and the portable carry case work across the whole range. Research use only.

Completing the setup

A pen is just one part of a reconstitution bench (a lab workstation where you dissolve a powder in liquid to make a working solution). You also need a 3 ml glass cartridge to hold the finished solution, and bacteriostatic water as the diluent (the liquid used to dissolve the powder). Bacteriostatic water has a small amount of preservative added to stop bacteria from growing in it. If you are starting from scratch, the complete starter kit bundles the pen, cartridges, and water together.

For the math behind filling a cartridge and carrying leftover solution forward, see our reconstitution and blend calculators.

Reminder: research and educational reference only. Preppin Peppers sells hardware and materials, not peptides. Not medical, dosing, or health advice, not evaluated by the FDA, and not intended for human or animal use.

Frequently asked questions

What cartridges does the Gansulin metal reusable pen use?

The Gansulin pen uses standard 3 ml (300-unit) glass cartridges conforming to ISO 11608-3, the same size used by most reusable research pens, keeping refill costs low and supply straightforward.

How does the Gansulin pen's dose mechanism differ from the V1, V2, and V3 pens?

The Gansulin uses a precision click-dial knob plus a spring-driven auto-inject button. The V1 and V3 use precision click-dial with manual push delivery; the V2 uses a draw-and-push (pull-to-set, push-to-dispense) plunger mechanism.

What is the dose range and increment of the Gansulin metal reusable pen?

The Gansulin pen dials 1 to 60 units per draw in 1-unit increments, displayed in a clear unit counter window, allowing precise, repeatable volume selection without freehand syringe estimation.

V1 vs V2 vs V3: Full Specs Compared

If you are shopping for a reusable reconstitution pen (a lab tool that draws a set amount of liquid from a cartridge into a vial), five things decide whether it is worth buying: how it sets a dose, how far it can draw, what cartridge it takes, what it is made of, and who you are actually buying it from. This guide walks through each one, then tells you exactly which pen to pick.

1. How the pen sets a dose

This spec decides how the pen feels every single time you use it. It is also the one most product listings never bother to explain.

Our V1, V2, and V3 all use a draw-and-push method. You pull the end knob outward until a numbered scale shows the amount you want. You read that number in a small window on the side of the pen. Then you push the knob back in and the pen delivers that amount. Think of it like pulling back a syringe plunger to a mark, then pushing it forward. It is straightforward and easy to read.

The Gansulin works differently. You dial in your amount one click at a time, and each click makes a sound. Each click stands for one unit. Then you press a button, and a small internal spring pushes out the liquid. If you would rather count clicks than read a scale, this is the pen for you.

Many generic pens sold online never explain how their dial works at all. If a listing cannot describe its own mechanism, that tells you a lot about the company behind it.

2. Dose range and increment

One unit equals 0.01 ml (one one-hundredth of a milliliter, a very small amount). All four of our pens use this same standard and move up or down in single-unit steps.

Where they differ is in how far they can draw in one go. The V1 draws up to 80 units in a single set, which is the largest single draw in our lineup. The V2, V3, and Gansulin go up to 60 units, which is the standard ceiling for pens built around a 3 ml cartridge. If your bench work calls for a larger single draw without resetting the dial, the V1 is the only one that can do it.

3. The 3 ml cartridge standard

Every pen worth buying is built to fit a standard 3 ml (300-unit) glass cartridge. Think of the cartridge like a small ink tube inside a pen. Using a standard size keeps replacement cartridges affordable and lets you buy them from any seller, including us or anyone else.

One thing to watch: 3 ml cartridges come with different stopper lengths. The stopper is the small rubber piece at one end of the cartridge that the pen mechanism pushes against. Our V1 takes short-stopper cartridges. Check the stopper type before pairing a pen with cartridges you already own, because a mismatch will not seat correctly. Our 3 ml glass cartridges clearly state the format for exactly this reason.

If a pen only works with its own special cartridges, you are locked into buying from that one seller forever. Avoid that.

4. Build: metal, not plastic

The outer shell decides whether your pen lasts a year on the bench or gives out quickly. Our V1 has a metal body. The V2 and V3 are made of anodized aluminum (aluminum that has been treated to make it harder and more scratch-resistant). The Gansulin is all-metal, inside and out. Disposable plastic pens are sealed and thrown away after one use. They look cheap up front, but they quietly become the most expensive option per use over time.

Two build details are worth paying for, and almost no listings mention them:

• An overdraw stop, meaning the dial will not let you set a dose larger than what is left in the cartridge. The Gansulin documents this clearly.
• Dial-back correction, meaning you can reduce the amount you set without releasing a single drop. Also documented on the Gansulin.

5. Who you are buying from

This is the spec nobody lists, and it shapes all four of the others.

We buy directly from the manufacturers who build these pens. There is no importer, no distributor, and no middleman between the factory and your bench. That shows up in three concrete ways:

• Price. Every extra step in a supply chain (the path a product takes from factory to buyer) adds a cost. We cut out those steps, so our V1, V2, and V3 sell for $21.99, while comparable pens from resellers list at $24.99 to $26.99. Same class of hardware, fewer hands in the middle.
• Consistency. Buying direct means the same factory, the same equipment, and the same specs on every production run. You are not at the mercy of whatever a marketplace seller happened to source cheapest this month.
• Answers. We can tell you the stopper format, the dose mechanism, and the exact build of every pen on this page, because we work directly with the people who make them. Ask a marketplace reseller the same questions and see what comes back.

Everything ships new in factory-sealed retail packaging, from the USA, with tracking on every order and 30-day returns.

Which pen should you buy?

What about the cheap marketplace pens?

Generic plastic cartridge pens sell for under $20. That is the only thing they have going for them. In the listings we checked, none stated a dose increment, none mentioned an overdraw stop, and none named the factory that made them. If a pen is going to live on your bench for a year, saving a couple of dollars up front is not the number that matters most.

Before you buy: the checklist

1. Does the listing state the dose mechanism (exactly how the dial works)? If not, walk away.
2. Does it state the increment? The standard is 0.01 ml per unit.
3. Does it take standard 3 ml cartridges, and does it say which stopper length?
4. Is the body metal, and is there an overdraw stop?
5. Can you find out who actually made it?

Every pen on this page answers all five questions. That is the entire point of buying direct.

Shop the reusable pens →

Next: our walkthrough on how to load and prime a cartridge pen covers purging air, the most common source of dose error regardless of which pen you bought.

More in our reusable reconstitution pens collection.

What the research community gets wrong about reusable reconstitution pens

Reusable cartridge pens are simple hardware, but a few ideas about them get repeated online that do not hold up at the bench. Here is what is worth correcting.

• "Units" is a volume marking, not an amount of substance. On these pens one unit equals 0.01 ml of whatever liquid sits in the cartridge. The pen measures volume only. It does not know or read the strength of what you put in it.
• Reusable does not mean less accurate than disposable. The same delivery-accuracy test methods used for pen systems (ISO 11608-1) apply to refillable and single-use designs alike, and refillable cartridge pens have been measured against those same limits. A metal reusable body is not a step down in measurement.
• Stopper length is a real compatibility spec, not a detail. Two cartridges can both say 3 ml and still differ in stopper length. If the stopper does not seat against the pen mechanism, the counter reading will not match the volume that actually comes out.
• The counter window shows what you dialed, not what left the tip. Trapped air is the common reason the two differ. Priming the pen until liquid appears is what makes the dialed number and the delivered volume line up.
• The metal build is about repeatability, not looks. The value of a firm clicking dial is that it returns the same volume across many cycles of bench use. That consistency over repeated draws is the point, more than the finish on the outside.

From our bench: we like to sanity-check a pen the honest way. Fill a cartridge with plain water, prime out the air, dial a set number of units, and dispense onto a lab balance, since 1 ml of water weighs about 1 gram. If you run this on your own pen, tell us how the mass you measured compared to the volume you dialed. We would rather publish your real numbers than a spec sheet's.

Sources

1. Bacteriostatic Water for Injection, USP , FDA/DailyMed label (0.9% benzyl alcohol)
2. Duerkop et al., Biotechnol J 2018 , Impact of Cavitation, High Shear Stress and Air/Liquid Interfaces on Protein Aggregation
3. Sigma-Aldrich (Merck) , Handling and Storage Guidelines for Peptides and Proteins
4. Abdel-Tawab et al., J Diabetes Sci Technol 2015 , Dosing Accuracy of Two Disposable Insulin Pens According to ISO 11608-1:2012
5. Clarke & Dain, Expert Opin Drug Deliv 2006 , Dose accuracy of a reusable insulin pen with an integrated plunger mechanism
6. Krzywon et al., Curr Med Res Opin 2010 , Dosing accuracy of commonly used disposable insulin pens (1 U to 60 U range)