2 x original Apple T8 pan head grey 11mm screws for the PowerBook 500 series and Powerbook Duo range. Four of these are used on the bottom case of the 500 series, one secures each of the clutches to the chassis, one secures the hard disk bracket.
On the PowerBook Duo, there are four on the bottom case, two secure the logic board through the battery connector and one secures each clutch bracket to the chassis.