# Exact Input and Exact Output (/docs/protocols/uniswap-labs-hooks/erc4626-wrapper/concepts/exact-input-and-exact-output)

Learn which swap types ERC4626WrapperHook supports and why exact-output swaps revert.

* **Exact input is supported** in both directions.
* **Exact output is not supported** (`_supportsExactOutput` returns `false`). An exact-output swap would require minting an exact number of shares, which `vault.deposit` cannot guarantee. Exact-output swaps revert with `ExactOutputNotSupported`.

Integrations should always construct wrapper hops as exact-input.