The drill bit is made of carbon steel and the countersink is made of good quality 45# steel, which ensures a long service life The combination drill bit and countersink drill bit are perfect for drilling, chamfering, #39;deburring and milling There are 10 sizes of 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 7mm, 8mm, 10mm and you can choose the one you need The design five flute provides small chip loads and faster removal, it can discharge sawdust more quickly and smoothly Suitable for drilling holes in low hardness boards such as such as wood, plastic and other soft materials LRFR is committed to providing each customer with the highest possible quality of customer service.