A slide tray is a device, also known as a magazine or holder, used to organise and feed slides into a projector. The common type is the Universal (U) tray, a straight magazine with a capacity of 36 or 50 slides, suitable for collections with mounts of varying thickness. The CS system, developed by Agfa, is designed for thin CS mounts and can hold 100 slides in the same space as a 50-slide universal tray, with grooves that lock the slides securely even when the tray is inverted. Another option is the LKM tray, designed by Leitz Kindermann, which can hold 80 slides of any make with mounts up to 1.6mm thick, taking up the same space as a 50-slide universal tray. Slide trays help photographers and presenters efficiently organise, store, and project slides while maximising capacity.