Description: These self centering drill bits put hinges right where they should be in the center. 4 of the most often used sizes for carpenters, cabinet, furniture makers and other wood working trades. Positioning accuracy, will not shift, the chips will automatic discharge from the hole on either side of the top of the drill, not stuck drill. Easy to use and install. 5/64'': Hole diameter is about 2 mm, Use about 2.2 - 2.8 mm tapping screw 7/64'': Hole diameter is about 2.8 mm, Use about 3 - 3.5 mm tapping screw 9/64'': Hole diameter is about 3.5mm, Use about 4 - 4.5 mm tapping screw 11/64'': Hole diameter is about 4.5mm, Use about 5 - 5.5 mm tapping screw Specification: 5/64'': Length: Approx. 58.56mm/ 2.31inch 7/64'': Length: Approx. 88.11mm/ 3.47inch 9/64'': Length: Approx. 94.62mm/ 3.73inch 11/64'': Length: Approx. 94.62mm/ 3.73inch Material: Brass, HSS Color: Silver Package Includes: 4 Pieces self centering bits hinge wood drill bit tool set Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement. If making soft wooden, you can choose a smaller size. If the hard one, please choose corresponding or the bigger size