We offer several types of competent cells for use in recombinant DNA cloning experiments such as library preparation, recombinant plasmid preparation, or subcloning. Several of our E. coli chemically competent cells can be used for general-purpose cloning, including JM109, HB101, and DH5 alpha, while the rest of our offerings can be used for specific applications. HST08 is used for cloning methylated DNA and large DNA fragments, including fragments greater than 10 kb, while HST16CR is a low-copy-number derivative of HST08 useful for working with toxic genes. HST02 can be used as a host for M13 phage or for library preparation or subcloning and CJ236 is used for preparing single-stranded uracil-containing DNA for selecting site-directed mutations by Kunkel's method. Finally, BMH71-18 mutS (product availability varies by region) can be used for site-directed mutagenesis and MV1184 is useful for selecting amber mutants.