The BcaBEST DNA labeling kit is a novel random-primer labeling system that uses longer primers (9-mers) and BcaBEST polymerase, a thermostable DNA polymerase isolated from Bacillus caldotenax. Unlike the E. coli Klenow fragment (Feinberg and Vogelstein 1983; Feinberg and Vogelstein 1984) or modified T7 DNA polymerase, Bca polymerase allows stable polymerization of DNA even for templates with high GC content containing highly structured regions. Longer 9-mer primers increase the incorporation efficiency of labeled nucleotides up to 80%.