FAQ: Do I need to spike in custom sequencing primers when sequencing libraries made with NEBNext Multiplex Oligos for Illumina (Unique Dual Index UMI Adaptors DNA Set 1) on the Illumina platforms? 

No. Libraries made NEBNext Multiplex Oligos for Illumina (Unique Dual Index UMI Adaptor DNA Set 1) are fully compatible with Illumina sequencing protocols of TruSeq HT libraries. For HiSeq, HiScanSQ, or GAIIx systems on single-read flow cells, the TruSeq Dual Index Sequencing Primer Box, Single Read (single use box) (catalog # FC-121-1003) will need to be ordered separately when using both indices. This add-on box is not required with the MiSeq System or on paired-end flow cells for HiSeq, HiScanSQ, GAIIx.  Please refer to Illumina website for complete information.