#3 Square Drive Bit - 50mm. Commonly used with heavier gauge decking screws. The vertical sidewalls create a positive engagement between the fastener and bit which is very effective in reducing cam-out. Length can be extended via a Drive Bit Extension Quick Change Adapter.
Most decking screws require a #2 drive bit. The #3 is used with the Bremick Wing Self Drilling B8 14G x 50mm Decking Screws.