Sony A7R III (ILCE-7RM3) Eyepiece Cover FDA-EP18 EVF Viewfinder Eyecup
Sony A7R (ILCE-7R), Alpha 99 II (α99 II ILCA-99M2), A7 III (ILCE-7M3 / ILCE-7M3K), A7R IV ILCE-7RM4, A7R III (ILCE-7RM3). They also play an important role inpreventing any stray light from entering the viewfinder whilst you’re looking down it.