These are replacement 4mm, pilot drill bits for the FISCH multi-functional Forstner bits. They come in packs of 3, either 40mm or 63mm long. Which size you choose depends on the diameter of the Forstner bit you intend to use and the intended angle of attack. Forged from one piece of high quality tool steel for extra strength, the shanks of these drill bits have a self-locking taper matching the tapered socket in the centre of the multi-functional Forstner bit. Once inserted into the socket they are very secure and run true. To replace the pilot drill or exchange it for a centre point we recommend the FISCH point removal tool. Made in Europe.