Countersinkin..

SMART-BIT consistently makes a perfect hole and fit every time. it is designed and manufactured specifically for deck builders working with hardwood or composite materials and using stainless steel screws that require pre-drilling and countersinking. Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.
Is Discontinued By Manufacturer ‏ : ‎ No
Product Dimensions ‏ : ‎ 4.7 x 0.2 x 3.5 inches; 4.8 ounces
Item model number ‏ : ‎ Bda166
Date First Available ‏ : ‎ February 10, 2011
Manufacturer ‏ : ‎ Starborn Industries, Inc.
ASIN ‏ : ‎ B004AQ6QBW

For use with #10 SMART-BIT tools|Parabolic Fluted Bits|5 Replacement Bits|For Decks and Woodworking