Product formed from a ceramic material, at least part of the said product not being formed from amorphous silica and including pores and satisfying the following criteria (a), (b) and (c): (a) at least 70% by number of the said pores are frustoconical tubular pores extending substantially parallel to each other in a longitudinal direction; (b) in at least one cross-section plane, the mean size of the cross sections of the said pores is greater than 0.15 μm and less than 300 μm; (c) in at least one cross-section plane, at least 50% by number of the pores have a convexity index Ic of greater than 87%, the convexity index of a pore being equal to the ratio Sp/Sc of the surfaces Sp and Sc delimited by the perimeter and by the convex envelope of the said pore, respectively.