Case

A case is a container item holding a fixed pool of skins, usually organized into rarity tiers (Mil-Spec, Restricted, Classified, Covert, plus a Special/knife-or-glove tier). Opening one — historically with a matching purchased key, though Steam now also offers a keyless fee-based unlock — awards exactly one skin from that pool at random, with each tier far less likely to drop than the one below it.

Cases are the primary way most non-rare skins enter the economy in the first place, and a case's pool is permanently fixed once retired, which is part of why skins from older, discontinued cases can hold or gain value over time even at common rarity tiers.