Nanocrystalline magnetic cores come from nanocrystalline steel. Specifically, this steel features a crystalline structure with individual grains measuring no more than 70 nm. Moreover, we process FeCuNbSiB material using thermal T or thermomagnetic T+H fields. As a result, these techniques allow us to create cores with various magnetic properties. Furthermore, these special tapes rank among the most advanced soft magnetic materials available. They exhibit very low magnetic losses and minimal magnetostriction. Consequently, they are ideal for low-noise electrical applications and devices operating at high frequencies. In addition, the nanocrystalline tapes are used to build several types of magnetic cores, such as wound cores, wound cut cores, and stacked or block cores. The cores protection is provided by plastics, resins, or pressboard covers.