> 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/index-kits/library-preparation-index-kits-faq-list/000008026.md).
# Catalog/Reference numbers for IDT for Illumina DNA/RNA UD and Illumina DNA/RNA UD Indexes
For Illumina consumables, there are reference (ref) numbers at the kit, box, and tube/component levels. Orders are placed using the kit level catalog numbers. A single kit can contain multiple boxes, which in turn can contain multiple tubes or components. To simplify the purchasing experience, the Illumina website only displays the orderable kit reference or catalog numbers.
Below are the kit (blue), box (red), and component (black) reference numbers for the following Illumina index kits:
* Illumina DNA/RNA UD Indexes Sets A-D, Tagmentation
* Illumina RNA UD Indexes Sets A-D, Ligation
* \[obsolete] IDT for Illumina DNA/RNA UD Indexes Sets A-D, Tagmentation
* \[obsolete] IDT for Illumina RNA UD Indexes Sets A-D, Ligation
The "DNA/RNA…Tagmentation" kits include a single index plate each; whereas, the "RNA…Ligation" kits include the same respective index plate and also include an anchor plate. Each well of the anchor plate contains the same contents. Note that the IDT for Illumina DNA/RNA UD Indexes Sets A-D (20027213, 20027214, 20042666, 20042667) are obsolete, with last order date having been **January 30, 2025**. Illumina recommends ordering the new [Illumina DNA/RNA UD Indexes](https://github.com/illumina-swi/illumina-knowledge/tree/master/articles/Knowledge/Introducing-the-Illumina-DNA-RNA-UD-Indexes/README.md) (20091654, 20091656, 20091658, 20091660).
For more information on the differences between the Tagmentation and Ligation sets, and with which library prep kits they are associated, see the [Understanding the differences between Illumina index chemistries and anchor function](/library-preparation/general-library-prep/library-preparation-general-library-prep-reference_material-list/000006561.md) article.
The below index sets are currently obsolete; their information is provided only as a reference:
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| *For any feedback or questions regarding this article (Illumina Knowledge Article #8026), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000006561%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |
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