The IOP has 23,000 members split across four grades of membership: Associate Member (AMInstP), Member (entitled to use the postnominals MInstP), Fellow (entitled to use the postnominals FInstP) and Honorary Fellow (entitled to use the postnominals Hon.FInstP). Undergraduates, apprentices and trainees can become Associate Members, and qualification for MInstP is normally by completion of an undergraduate degree that is "recognised" by the institute – this covers almost all UK physics degrees. An MInstP can become an FInstP by making "an outstanding contribution to the profession" that is judged via double-blind and anonymous peer review.