One Shot® Stbl3™ Chemically Competent E. coli are designed especially for cloning direct repeats found in lentiviral expression vectors. The Stbl3™ E. coli strain is derived from the HB101 E. coli strain and is recommended for use when cloning unstable inserts such as lentiviral DNA containing direct repeats (e.g., Invitrogen® ViraPower™ Lentiviral Expression kits). The transformation efficiency of One Shot® Stbl3™ chemically competent cells is greater than 1 × 108 cfu/µg plasmid DNA.