Countersink Decking Tool suits trim head 10g or 4.80mm countersunk decking screws. It is a purpose designed pre-drilling and countersinking tool all in one Features / Benefits: The tool has a free spinning stop-collar with an o-ring which eliminates countersinking too deep protects the work surface and gives every countersink exactly the same depth. The drill bit is a powerbolic high-speed steel fluted drill bit that cut through decking more than twice as fast as standard wood bits. The tool offers an additional benefit of eliminating mushrooming (the formation of small mounds of waste material near the screw hole surface). The anit-clog design improves visibility and debris removal Ideal for: Timber decking (Hardwood and composite materials) blue board and woodworking Drilling into Hardwood: Some hardwood decking timbers can be extremely hard and dense so pre-drilling the timber may be the only satisfactory way to install decking screws. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person and Bolt and Nut Australia is not responsible for any loss claim for damages arising therefrom.