Collections in Counter-Strike 2 are curated sets of weapon skins that share a common theme. Each collection contains skins across multiple rarity tiers, from Consumer Grade to Covert. Collections determine which skins can appear as trade-up contract outcomes. Only skins from the same collection can result from a trade-up.

When you submit a trade-up contract, the output skin is drawn from the same collection as your inputs, one rarity tier higher. By choosing inputs from collections with valuable higher-tier skins, you can maximize your expected profit. The Trade Up scanner does that search across the whole market, and you can try combinations yourself in the Trade Up calculator.