tip for better work. Good design: U-shape groove is great for the discharge of wood chips, to improve the drilling efficiency. Various dill bits: the set contains different size drill bits, enough, satisfied for multiple demands. Wide application: it works with mortising machine, very suitable for drilling wood, like MDF, particle board, pine wood, basswood, etc. Total 5 Combinations for Option 4pcs: 1/4 inch (6.4mm), 5/16 inch (8mm), 3/8 inch (9.5mm), 1/2 inch (12.7mm) 5pcs: 1/4 inch (6.4mm), 5/16 inch (8mm), 3/8 inch (9.5mm), 1/2 inch (12.7mm), 5/8 inch (16mm) 6pcs: 1/4 inch (6.4mm), 5/16 inch (8mm), 3/8 inch (9.5mm), 1/2 inch (12.7mm), 9/16 inch (14mm), 5/8 inch (16mm) 7pcs: 1/4 inch(6mm), 1/4 inch (6.4mm), 5/16 inch (8mm), 3/8 inch (9.5mm), 2/5 inch (10 mm), 1/2 inch (12.5mm), 1/2 inch (12.7mm) 7pcs: 1/4 inch (6.4mm), 5/16 inch (8mm), 3/8 inch (9.5mm), 2/5 inch (10 mm), 1/2 inch (12.7mm), 9/16 inch (14mm), 5/8 inch (16mm) Specification: Material: Carbon Steel Color: Silver Type: 4pcs / 5pcs / 6pcs / 7pcs / 7pcs (Optional) Package Size: 4pcs: 22*11*3cm / 8.66*4.33*1.18in 5pcs: 22*13*3cm / 8.66*5.11*1.18in 6pcs: 22.5*8.5*5.5cm / 8.85*3.34*2.16in 7pcs: 22*13*5.5cm / 8.66*5.11*2.16in 7pcs: 22.5*13*5.5cm / 8.85*5.11*2.16in Package Weight: 4pcs: 670g / 23.63oz 5pcs: 910g / 32.09oz 6pcs: 1140g / 40.21oz 7pcs: 1144g / 40.35oz 7pcs: 1300g / 45.85oz Note: Drill bits set only, other accessories in the pictures are not included. The bit is not suitable for processing metal, glass, plastic, concrete, gypsum board etc. Due to lighting or other reasons, the picture and material object may slightly differ. Due to manual measurement, there may be deviation, please in kind prevail. Packing List: 4 * Drill Bit