# How many extra cycles are included in NextSeq 500/550 reagent cartridges?

There are extra cycles (17 or 18, depending of the kit) included in NextSeq 500/550 reagent kits that can be used for index reads or to extend insert read lengths.

* 75 cycle kits: 92 cycles total
* 150 cycle kits: 168 cycles total
* 300 cycle kits: 318 cycles total

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