The reflex finder RM2 (52183) adjusts +/- 5 D but the flex body 903SWC version RMfx (72530) does not and optician supplied are needed.
PM90 uses interchangeable but the PME90 -2 to +0.5 are built in with std. additions possible. The PME45 has a built in diopter correction of -2 to +1
Also the range of interchangeables quoted is correct except for the PME90 version which runs -4.5 to +3.