> For the complete documentation index, see [llms.txt](https://spire-docs.gitbook.io/spire/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://spire-docs.gitbook.io/spire/based-stack/sequencing-revenue-mev-retention.md).
# Sequencing revenue (MEV) retention
Spire introduces a sequencer election model that prioritizes sequencers that are willing to pay to sequence a block, thereby returning some value to the application.
> Today, applications leak millions of dollars to their sequencers.
We expect that the total amount of sequencing value returned to the application through this mechanism will be on the order of the expected value of sequencing that appchain. In practice, this could be millions of dollars for some types of applications and may end up being very little for others. Because of this disparity, MEV retention is something we want to be flexible with and allow applications to parameterize.
Priority fees and other gas fees that users pay to be included in a block are detectable within the execution environment. This means that implementation here can be done in the execution environment, not on the sequencing layer.
These types of fees can be trivially parametrized to be more flexible for different apps. We are continuing to do research into the numbers that make the most sense for most applications.
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