# 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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