# Optimal cluster density guidelines for the NextSeq 500/550

The recommended raw cluster density for NextSeq 500/550 High-Output and Mid-Output runs is 170-220k/mm2 for well-balanced, base diverse libraries (eg, whole genome libraries, RNA-seq libraries, etc.).

For further information, search for Knowledge Base articles:

* **Cluster density guidelines for Illumina sequencing platforms.**
* **How to achieve more consistent cluster density on Illumina Sequencing Platforms.**

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #2067), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000002067%20-%20Instrumentation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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