Applicant has discovered a new zeolite containing composition and a process for preparing the same. The composition is unique in that the zeolite crystals making up one layer of the composition pack in a manner such that the composition is essentially continuous with no large scale voids even when the zeolite layer is <10 .mu.m thick. Thus, the present invention is directed toward a composition comprised of a porous substrate and a layer of zeolite crystals wherein said layer of zeolite crystals is a polycrystalline layer with at least 99% of said zeolite crystals having at least one point between adjacent crystals that is .ltoreq.20 .ANG. and wherein at least 90% of said crystals have widths of from about 0.2 to about 100 microns (preferably about 2 to about 50 microns) and wherein at least 75% of said crystals have a thickness of within 20% of the average crystal thickness. Preferably the composition has at most 1 Volume % voids in the zeolite layer. Use of the composition is also described.