vls – slimline vision lite for 3/16-1/4 glass low profile beveled vision lite for fire-rated doors. Self-attaching frame has single-sided fasteners. fire-rated air louvers glazing to fit this product: ws, ul, kfrf, ppf, pyro. fire-rating, testing & listings: when installed in properly rated and approved door, ratings up to 3 hours can be achieved, depending on the glazing used. See glazing ratings for maximum exposed area. Tested and listed for ul 10c and criteria of ubc 7-2 positive pressure.