# Permanent Fee (/docs/protocols/uniswap-labs-hooks/volatile-pair/concepts/permanent-fee)

Understand how VolatilePair moves the ask and bid permanent fees toward the last price move while keeping their total fixed.

Each side of a VolatilePair pool has a permanent fee. The ask and bid permanent fees always add up to the pool's resting spread.

## How the fee changes
On the first swap of a new block, the hook measures the price impact since the previous block's open. It then raises the leaning side by a step:

```
step         = min(skewRate × priceImpact, maxSkewStep)
newLeanPerm  = min(oldLeanPerm + step, maxSkew)
backrun perm = restingSpread - newLeanPerm
```

The backrun side goes down by the same amount the leaning side goes up. Both sides stay within `[restingSpread - maxSkew, maxSkew]`.

The new values persist until the price moves again.

## Purpose
Informed flow tends to trade in the direction of the last price move. A higher fee on that side reduces loss-versus-rebalancing (LVR) for LPs. The total spread stays the same.

## Parameters
| Parameter       | Effect                                       |
| :-------------- | :------------------------------------------- |
| `skewRateE6`    | Permanent fee step per unit of price impact. |
| `maxSkewStepE6` | Maximum step in one block.                   |
| `maxSkewE6`     | Maximum permanent fee on either side.        |

`maxSkewE6` must be between half the resting spread and the full resting spread. If `maxSkewE6` equals the resting spread, a long enough trend can bring the backrun side's permanent fee to zero. The temporary fee and the mid-block extra still apply.

## Where to Go Next
* [Temporary Fee](/docs/protocols/uniswap-labs-hooks/volatile-pair/concepts/temporary-fee)
* [Pool Creation and Configuration](/docs/protocols/uniswap-labs-hooks/volatile-pair/concepts/pool-creation)