We observe unusually strong magnetoresistance commensurability oscillations in two different types of artificial arrays of scattering centers, multiparallel focusing slits and a square antidot lattice, both fabricated on a two-dimensional electron gas by electron-beam lithography and damageless wet etching. The strength of the magnetoresistance peaks is attributed to a high reflection specularity and a small effective antidot cross section. The absence of commensurability effects near Landau level filling factor&ugr;=3/2is attributed to the composite fermion mean free path being smaller than the slit and antidot spacings. The mechanism for the observed commensurability is discussed. ©1997 American Institute of Physics.