The ER1 3.175 is a milling tool for Iecho machines made from the finest of metals, years of research and extensive testing (that no human could withstand),  but it prevailed and though this testing and countless trials that has been put into this bit to make sure it has what it take to hold the name Iecho, the most durable bit you will use, its 3.175 mm tip will be able to get high precision pieces of art out of your Iecho machines router attachment