I’m shocked hahah I learned about this method from someone on this forum… I thought it was a public post but maybe it was a DM.
I think it’s just a standard 20g needle for most typical injections. The important part is that a path is cut through the encapsulation so the implant can squeeze its way out.
Some professional body modders / piercers have done this using a 8g or 6g needle… it leaves quite the hole but it does seem to work.