Hexalobular (6 Lobe) socket flat countersunk head partial thread and cutting ribs under the head — 3,5 x 30 / 18 (X15)

Bossard · Direct Assembly Screws for Wood. d1: 3,5 | L: 30 | d2 max.: 7 | k max.: 2,15 | Hexalobular socket: X15 | b: 18