# What do (S), (M), and (L) mean in Illumina library prep kit names?

A few Illumina library prep kits have a single letter in parentheses as part of the library prep kit name:

* Illumina DNA Prep with Enrichment, (S) Tagmentation
* Illumina DNA Prep, (M) Tagmentation
* Illumina RNA Prep with Enrichment, (L) Tagmentation

These letters refer to the general size of the resultant library fragment post-tagmentation. S stands for "small," M for "medium," and L for "large" insert sizes.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #6971), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000006971%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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