The pens are reusable. You reconstitute a peptide, draw into a syringe, then fill a new pen cartridge (with a filter), and put it in the pen.
Once it's in the pen, pinning is a 30sec ordeal. You clean the end of the cartridge, put on a needle (or reuse as you see fit), and jab/click. Easy.
You really have to have a pen for each 'tide you're pinning. Swapping the cartridge for multiple 'tides would take away any of the convenience.
I bought my first pen because the GHK-Cu I was pinning was quite painful. I had read that pinning in the glutes was much less painful. Hard to do that with a diabetic syringe!
But in the time I waited for the arrival of the pen, I found a spot about 2" lower where there is no pain, so I've just been using the pen there.
Pros: They do hurt less. My pen needles are smaller than my diabetic syringes. If you're squeamish, you can buy a V2 pen and you don't even see the needle. They are convenient. Time saver. Fiddly to fill and prep once, but then super easy for the rest of the 3ml vial. I think it raises less eyebrows at a security checkpoint to see a few pens in a case vs a pile of vials of unlabeled white powder and diabetic syringes. (The checkpoints I have to clear aren't just at airports).
Cons: they cost. Not a lot, but when you've got 8 or so, it adds up. You have to buy cartridges. But if you're filtering, you'd need either those or sterile vials to transfer your 'tides into after reconstituting, so that extra cost is irrelevant.
