We report on the properties of submicrometer-sized Josephson tunnel junctions fabricated in a cross-type technology. The quality of the junctions is indicated by current density profiles obtained from the Fraunhofer diffraction patterns. The capacitance of the junctions is determined by the evaluation of Fiske steps. The strong improvement of SQUID parameters, like the usable voltage swing and the intrinsic flux noise due to the use of these low capacitance Josephson tunnel junctions, is shown on SQUID magnetometers. In addition, a very high stability against magnetic fields of up to several mT during cooling down and unshielded operation is demonstrated.