Part# 26310 is the BAK G2 Tonneau Cover, which uses composite panels with aluminum skins and a satin powder coat finish and is BAK's standard tonneau cover. Part# 35310 is BAK's HD Tonneau Cover which uses fully aluminum panels for extra strength. Part# 126310 is BAK's Fibermax Series Cover which uses Fiberglass Reinforced Polymer panels to save some weight while still being strong.