# Overview of the IDT for Illumina RNA UD Index Sets, Ligation

The IDT for Illumina RNA UD Indexes Sets A, B, C, and D, Ligation (catalog numbers 20040553, 20040554, 20040555, and 20040556 respectively) include an IDT for Illumina DNA/RNA UD Index primer plate as well as an RNA Index Anchor plate.

* These index kits are compatible with the [Illumina Stranded mRNA](https://www.illumina.com/products/by-type/sequencing-kits/library-prep-kits/stranded-mrna-prep.html) and [Illumina Stranded Total RNA](https://www.illumina.com/products/by-type/sequencing-kits/library-prep-kits/stranded-total-rna-prep.html) library preparation kits.
* The RNA Index Anchors are **required** for compatibility with the above workflows.
* The Index Anchors are short adapters that are ligated to provide the binding site for the index primers.
* The anchor sequences are the same for the entire plate (the contents of all index anchor plate wells are identical).
* The RNA Index Anchors are **not** the same as the UMI DNA Index anchors (found in IDT for Illumina UMI DNA/RNA UD Indexes Set A, Ligation, which are compatible with the [TruSight Oncology 500 HT](https://www.illumina.com/products/by-type/clinical-research-products/trusight-oncology-500-ht.html) library preparation workflow.)

**Note**: the primer plates are labeled "IDT for Illumina **DNA/RNA** UD Indexes" despite being bundled within the IDT for Illumina **RNA** UD Indexes kits.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #6081), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000006081%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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