The flat cardboard slide mailers feature an inner finger groove for effortless slide removal along with a cover that opens for viewing. They securely hold slides with or without a cover-glass. The flat surface area is ideal for labeling or writing any necessary information. Light-weight and reusable to minimize cost. The 20-place cardboard slide holder contains a numerical index that corresponds to the inner slide compartments. 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.