SMRT sequencing allows for real-time imaging of fluorescently tagged nucleotides that are synthesized along individual DNA template molecules. The sequencing reaction ends when the template and polymerase dissociate. The average read length from the PacBio instrument is approximately 2 kb, and some reads may be over 20 kb.
https://www.cd-genomics.com/PacBio-SMRT-Sequencing.html