307505003 Tool-less Tension Nut Assembly replaces 678618002 Homelite & Ryobi 36cc-42cc chainsaws by Homelite Genuine OEM Replacement Parts Compatible with Homelite Chainsaw Tightens and secures the chainsaws clutch cover lock knob Made out of metal with plastic This part is a merged assembly of old part# 518769001 (Cover Knob) and 678618002 (Tension Nut).