This pack of 5 internal diameter 1.375"/35mm caps allows you to protect most brands of Plossl eyepieces including Orion and older Meades (but not Televue plossls). They also fit Televue Nagler 4.8mm and Edmund RKE eyepieces. They fit on the objective end of the eyepiece that you place your eye to. They are made of soft yellow plastic so they are quick to put on and take off, and easy to see in the dark.