Peptide pen formats: reusable pen, disposable pen, cartridge and vial
The catalog lists research peptides in four formats. This guide says what each format is, what a listing in that format ships as, and how the formats relate to each other.
Published October 11, 2026 · For laboratory research only
The four formats at a glance
| Format | Brand | What it is | A listing ships as |
|---|---|---|---|
| Reusable pen | EJ | A peptide pen that takes replaceable cartridges | One reusable pen and one cartridge of the listed product |
| Refill cartridge | EJ | A cartridge for the EJ reusable pen | One cartridge |
| Disposable pen | EJ | A prefilled peptide pen, sold as a single sealed unit | One prefilled disposable pen |
| Vial | Robin | A vial from the supplier Robin, listed with its package volume | One vial in the chosen strength |
Every product is listed for laboratory research only.
Reusable pen
An EJ reusable pen comes apart into five parts: the cap, the refill cartridge, the collar, the body and the end knob. The cartridge is the part that holds the material, and it is the part that is replaced.
Each reusable pen listing names one product and one strength. It ships as one reusable pen and one cartridge of that product, so the first cartridge is included.
Refill cartridge
EJ refill cartridges are made for the EJ reusable pen and are sold separately from it. A cartridge listing names one product and one strength, and ships as the cartridge alone.
The catalog lists cartridges for the EJ reusable pen only. Check the product details against your pen before you order.
Disposable pen
An EJ disposable pen is prefilled and sealed, with the material inside the pen body. It is sold as one unit, and the catalog lists no separate cartridge for it. A listing ships as one prefilled disposable pen.
Disposable pen listings name the product and its strength. Blends list the amount of each component.
Vial
Vials in the catalog come from Robin, a separate supplier, and are listed under the Robin name. Each listing names the product, its strength and the vial’s package volume. Where a product is offered in more than one strength, the page lets you pick one and shows the price for it.
Robin’s own lab reports are linked on a vial’s page where the report names the same product and strength.
How strength is stated
Strength is stated in milligrams (mg). For a blend, the page lists the amount of each component as well as, or instead of, the total.
Lab reports by format
The lab report library opens without an account and can be searched by product, strength or lot. Robin vials link the supplier’s own reports. For some EJ pens and cartridges, the product page shows a reference record from a previous supplier, labelled as a reference that does not verify the EJ product or its batch.
To make sense of a report, see how to read a peptide COA.
Common questions
Does a reusable pen come with a cartridge?
Yes. Each reusable pen listing ships as one pen and one cartridge of the listed product.
Can a cartridge be bought without a pen?
Yes. Refill cartridges are listed separately, by product and strength.
Does a disposable pen take refill cartridges?
No refill is listed for it. A disposable pen is sold as one prefilled, sealed unit.
Which pens do EJ cartridges fit?
The catalog lists them for the EJ reusable pen. It makes no statement about other pens.
Where are the lab reports?
In the lab report library, and on a product page where a report names that product and strength.