Nikon EDG Series Instruction Manual page 30

Eyepieces
Jp
En
De
Fr
Es
It
Ru
FEP-20W
TS ring
attachment
Screw either attachment into the eyepiece for use.
30
FEP-38W
DS ring
attachment
FEP-30W
FEP-50W
FEP-25LER
FEP-75W
FEP-20-60