A porous refractory product includes a matrix of sintered silicon carbide having a porosity of about 45% to about 65%. The matrix is formed by heating in a noble gas atmosphere a cast preform including a mixture of alpha-silicon carbide and boron carbide each having a particle size of less than about 1 micron. The heating causes the formation of gaseous SiO within the silicon carbide matrix, which, in turn, forms pores having an average size of less than about 1 micron. The porous refractory products herein are suitable for use in a variety of applications including for use in high temperature particulate filtering applications.