A 3 ml pen cartridge is a borosilicate glass tube holding 300 units on a U-100 scale, closed by a crimped aluminium cap over a rubber septum at one end and a sliding rubber plunger at the other. It is an open industry format, not a proprietary one, so the same cartridge fits the Gansulin pen and the V1, V2 and V3 pens.
The 3 ml / 300-unit standard
3 ml is the near-universal pen cartridge size, and it is the reason cartridge pens are worth owning at all. Because the format is standardised, a cartridge is a commodity rather than a captive consumable: no pen manufacturer controls the supply, and no seller can strand you by discontinuing a line. If you see the format written as 3cc, that is the same thing. A cubic centimetre and a millilitre are identical volumes, and 3cc, 3 ml and 300 units all describe this cartridge.
The 300-unit figure comes from the U-100 scale: 100 units to the millilitre, so one unit is 0.01 ml and a full 3 ml cartridge reads 300. That is also why a 60-unit pen empties a cartridge in five full draws rather than one.
What the cartridge is made of, and why it matters
Borosilicate glass, not soda-lime. Borosilicate is chosen for low ion leaching and thermal shock tolerance, which is what keeps the container from contributing anything to what is inside it. The crimp cap is aluminium over a rubber septum designed to reseal after a needle passes through it, and the plunger at the base is a rubber piston that the pen's lead screw advances.
Two practical consequences. First, the septum tolerates repeated entry but not unlimited entry; each puncture takes a small core out of it, and a visibly chewed septum is a cartridge to retire. Second, the plunger is the seal, so a cartridge that has been stored with the plunger driven hard against the base for months can drag on first use.
Which pens these fit
Any pen built around the standard 3 ml / 300-unit cartridge. That includes every pen PreppinPeppers sells: the Gansulin click-dial pen, the V2 and the V3. The V1 pen takes the short-stopper variant of the format, so if you are buying cartridges specifically for a V1, check that detail rather than assuming. It is the single most common fitment mistake in this category, and it is the reason we call it out here rather than burying it.
If you are running a pen from another supplier, the format is still the format. Send us the pen model before ordering and you will get a straight answer about whether it fits, including a no.
Pack sizes, and when not to buy bulk
Cartridges are stocked as a 10-pack and as bulk packs, with the cost per cartridge falling as the pack grows. The variant picker on the product page carries the live sizes and pricing.
Bulk is the wrong call in two situations. If you have not yet confirmed the format suits your work, buy the smallest pack and find out first. And if you are buying for a V1 without having confirmed the short-stopper fitment, a bulk pack turns a small mistake into a large one. Buy ten, verify, then scale.
Packaging, storage and handling
Each cartridge arrives individually sealed in a self-sealing sterilization pouch carrying EO and steam process indicators. The pouch is the protective barrier, so a cartridge whose pouch is torn, damp or split should not be used. Note carefully that pouch indicators show a process was run; they are not a sterility certificate, and these are not sold as sterile medical devices.
Store sealed pouches in a clean, dry place at moderate room temperature, ideally below 75 degrees Fahrenheit (24 degrees Celsius), out of direct sunlight and away from high humidity. Humidity is the quiet enemy here: it degrades the pouch seal long before it touches the glass. Keep cartridges in the box they arrived in rather than loose in a drawer, where crimp caps get knocked.
Specifications
| Product type | Glass pen cartridge, empty |
|---|---|
| Capacity | 3 ml, which is 300 units on a U-100 scale, also written 3cc |
| Glass | Borosilicate |
| Closure | Crimped aluminium cap over a resealing rubber septum |
| Plunger | Sliding rubber piston, advanced by the pen lead screw |
| Packaging | Individually sealed in self-sealing sterilization pouches with EO and steam process indicators |
| Fits | Standard 3 ml cartridge pens, including the Gansulin, V2 and V3. V1 requires the short-stopper variant |
| Storage | Sealed pouch, clean and dry, below 75 degrees Fahrenheit (24 degrees Celsius), out of sunlight |
| Intended use | Research, educational, and demonstration use only |
Pairs with: any pen in the research pens collection, and bacteriostatic water as the diluent. A pen, cartridges and diluent bought together are the starter kits.
Common questions
Do these cartridges fit V1 and V2 pens?
The V2 takes the standard 3 ml cartridge directly. The V1 takes the short-stopper variant of the same 3 ml format, so confirm that detail before ordering a large pack for a V1.
Is a 3cc cartridge the same as a 3 ml cartridge?
Yes. A cubic centimetre and a millilitre are the same volume, so 3cc, 3 ml and 300 units on a U-100 scale all describe this cartridge.
Are the cartridges supplied empty?
Yes. They are empty glass cartridges. Any diluent is bought separately and nothing is pre-filled.
What are they made of?
Borosilicate glass with a crimped aluminium cap over a rubber septum, and a sliding rubber plunger at the base.
How should cartridges be stored?
Sealed in their pouches, clean and dry, at moderate room temperature below 75 degrees Fahrenheit (24 degrees Celsius), away from direct sunlight and humidity. Do not use a cartridge whose pouch is torn, wet or damaged.
Are these sterile?
No. The pouches carry EO and steam process indicators, but these are sold for research, educational, and demonstration use only and are not validated-sterile medical devices.
From The Lab
Everything in this collection is sold for research, educational, and demonstration use only. Nothing here is a medical device, nothing is sold sterile, and nothing is for human or veterinary use of any kind. Not evaluated by the FDA. Nothing on this page is dosing guidance. 21+.
