I have never ever used one but want to some day. I use pacifiers but is the NUK 5 niple really big or what. I looked on the site and codent find out for sure.
Nuk4 was designed for teenagers, Nuk5 is for adults. Both are for that speech therapy stuff.
When i received mine from PacifiersRUs.com, they also included a little manual describing it's usage. I dont recall the entire thing off my head, but i do recall it has to do with restoring speech impediments after patients have come out of long term comas. It also helps deliver feeding tubes into the mouth to restore chewing functions of the mouth. Not 100% sure on this, but i definitely remember seeing some of this in the manual provided with my paci.