Thermophilic Factor 55 (TF55, rosettasome) is a type II chaperonin occurring in Sulfolobus. Filaments composed of TF55 have previously been observed in vivo and in vitro, but the nature of the interactions between successive subunits has not been established. We have used cryo-EM to image a TF55 β subunit preparation isolated from Sulfolobus solfataricus, revealing filaments reminiscent of those seen in Sulfolobus shibatae. Averaging methods reveal that the oligomerisation surface relies on overlap of the helical protrusions, which matches contacts seen in previous crystallographic studies. Our findings further confirm hypothesises that filaments play a role in the regulation of chaperonin activity or Archeal cytoskeleton.