The spare part eye cup (643-0317) is compatible with: SLC 10x42 W B Gen. I (serial number D62... - D80...) Please note: this article can be ordered by piece. Should you need a set of two, please order a quantity of two eye cups. Manual for exchanging the eye cup: Removal - You only need to twist out & unscrew the old eye cup (counter-clockwise) by grasping the metal ring. Installation - when threading in replacement eye cup(s), turn them (clockwise) until they are fully tightened and flush with the binocular. Once they are flush, give them a final snug twist to fully seat and retain the eye cup.