Abstract: A protective cover for a photographic slide tray that is used with a slide projector. The cover is a thin disk of semi-rigid material having a large central opening and a generally imperforate annular marginal area which is superposed over circularly arranged separator walls which define slide holding slots in the tray. A flanged locking ring which holds the slides in the tray also secures the cover. The cover yields under the influence of the air blast from the projector cooling fan to minimize retardation of cooling air flow.