The NEBNext dA-Tailing Module has been optimized to efficiently incorporate a non-templated dAMP on the 3 ́ end of a blunt DNA fragment (1). 3 ́-dA DNA tailing prevents concadamer formation during subsequent ligation steps. DNA tailed with the NEBNext dA-Tailing module may be ligated to adaptors or cloning vectors with complementary dT overhangs. The NEBNext dA-Tailing Module is provided as a master mix to maximize efficiency and convenience in DNA sample preparation workflows. The NEBNext dA-Tailing Module has been validated by sequencing with the Il- lumina Genome Analyzer II (Illumina, Inc.) in conjunction with the NEBNext End Repair Module, NEBNext Quick Ligation Module and Phusion® High-Fidelity PCR Master Mix. For larger volume requirements, customized and bulk packaging is available by purchasing through the OEM/Bulks department at NEB. Please contact OEM@neb.com for further information.