> For the complete documentation index, see [llms.txt](https://knowledge.illumina.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://knowledge.illumina.com/library-preparation/amplicon-library-prep/library-preparation-amplicon-library-prep-faq-list/000005766.md).

# Can Illumina and IDT for Illumina DNA/RNA UD Indexes be used with the 16S Metagenomics Protocol?

**Yes**, the Illumina DNA/RNA Unique Dual (UD) Indexes and IDT for Illumina DNA/RNA UD Indexes can be used with the [Illumina 16S Metagenomic Sequencing Library Protocol](https://support.illumina.com/downloads/16s_metagenomic_sequencing_library_preparation.html). These indexes are compatible with the overhang sequences added in the first PCR step of the workflow.

When using the Illumina or IDT for Illumina DNA/RNA UD Indexes for the 16S workflow, use 10 µl of the pre-combined index primers per sample, rather than 5 µl each of the i5 and i7 Nextera XT index primers.

**Note:** The Illumina and IDT for Illumina DNA/RNA UD Indexes are 10 bp each; whereas, the Nextera XT indexes are 8 bp each.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #5766), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000005766%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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