Well, all venting requirements differ, but for a job requiring high efficiency and easy cleaning, our Lektromesh core vents are great. They have optimum venting capacity, with less cleaning and retain a long life. For all types of uses, our stainless steel twilled screen vents are super. For example, a 150 mesh fine screen is perfect for fine sands, as in the shell molding process, while a 35 mesh screen is standard and works well for general use, as it has a high venting capacity. Stainless steel screen vents come in 24, 30, 35, 40, 50, 60x70, and 150 mesh. Perforated or staggered slot is also available. Another option is the sintered bronze or powdered metal screen, which is perfect for jobs using liquid. The sintered bronze maintains a shallow head and allows liquid to escape the mold, while the mold retains the shape desired.