The present application relates to an eyepiece for use with a viewing device. The eyepiece is configured to change the distance between a first edge of the eyepiece and a lens near a second edge of the eyepiece. The eyepiece includes a first element having a pin extending therefrom and a rotational axis having a first axial direction and a second axial direction. The eyepiece further includes a second element having a groove, the second element sharing the rotational axis and configured to rotate about the rotational axis relative to the first element. The groove comprises a first pin movement section and a second pin movement section. The groove further comprises a pin stopping section, the pin stopping section located between the first pin movement section and the second pin movement section. The pin stopping section is configured to prevent the second element from rotating relative to the first element.