From the applications point of view, the advantage of low density given by MgB2 material must be taken into consideration and, the generation of strong magnetic flux densities using MgB2 should be investigated. In this contribution, we have studied the magnetic properties of samples processed by a fast Spark Plasma Sintering machine that is able to produce dense and high quality MgB2 samples. Experiments were carried out both on small pieces of the samples and on large-sized samples performing trapped field measurements in a Field-Cooling process. For temperatures between 10 K to 30 K, the results show a strong dependence of the magnetic behavior of the large-sized samples to the applied magnetic field sweep rate, while nothing particular appeared on the small samples. As the magnetic flux density produced by MgB2 bulks is directly linked to the potential of the applications, we report the field produced at the surface of one single MgB2 sample of 30 mm diameter and the field produced inside a stack of two MgB2 samples of 20 mm in diameter. A generation of magnetic flux density (magnetic polarization µ0M) up to 4.80 T @ 10 K and 3.92 T @ 20 K inside the stack of the two MgB2 samples was observed under negative supporting field of –1.47 T and –1.95 T, respectively. According to these values, to their very low density and to their ease of manufacturing, MgB2 bulks are promising materials for the applications of superconductors.