More informationBOX WITH BICROMATED finish (more resistant to oxidation than simple zinc plating) Head with a smaller diameter for ideal use in fittings. Flat head- PoziSquare (PSD) with ACR Anti-Camout Recess (Anti-slip seat) Double angle reinforced head Robust body Waxed thread as optimal angles Slotted body Quick start screw tip PSD tip included free in each box Also suitable for use with PH, PZ and Robertson