Original Apple 8mm/13mm hard drive bracket standoff for all the iBook G3 Clamshell ranges. Three of these screw through the hard drive bracket at logic board positions ZH9, ZH17 & ZH18, and one supports the optical drive at logic board position ZH11. 8mm is the standoff height when fitted, 13mm is the overall height including the threaded portion. The hex width is 5mm.