BHO Cartridge Refills???

So I am planning on investing in my first vape pen.

After reading reviews I see a lot of people have problems with loading. I personally would like to make that process as easy as possible. At a few clinics I have seen a few options for pre-filled cartridges. So I was wondering would these be a shop thing for the pens they have on sell only? Or something more universal, based on size?

I plan to ask the shop next time I stop by but it would make searching a lot easier if I could get some more knowledge on it.

If these are brand specific tanks then plus side is I have extra tanks every time I buy one. What would the shelf time for something like that? Could I fill my own and let them sit around?

So if you could spare a moment of your time I would appreciate it.

I think that the pre filled carts fit any Ego style pens and I think they are disposable. I would definitely ask first.

You are right. They cleared up a lot of things that i did not know. I really wish it could be refilled but oh well. Thanks for your response.