Slide Mailer, Cardboard, for 20 Slides The flat 20-place cardboard slide holder securely holds slides with or without a cover-glass. They feature an inner finger groove for effortless slide removal along with a cover that opens for viewing. They are light-weight and reusable to minimize cost. It contains a numerical index that corresponds to the inner slide compartments and the inside flaps are recessed so that there is no contact or contamination between the slides and the cover when closed. With a 360? hinge, the cover folds flat underneath to save space when the holder is in use.