This roof vent cover is made with 5.0mm woven fabric double foiled aluminum XPE insulation which reflects up to 95% of radiant heat, durable ripstop UV resistant polyester fabrics and powerful N52 Neodymium magnets. This roof vent cover fits the MaxxAir Fan or Fantastic Fan with 16.5″ x 16.5″ flange. Comes with storage sack and installs easily with magnets. Instructions for installing the magnets for a vent/fan cover Remove the fan/vent flange from the interior of your van (most are attached with four screws). Place the window cover on a flat surface with the VanEssential tag side facing down Place the flange on top so that the flat surface rests on the cover Place the included magnets on the flange so that they snap into place with the magnets inside the fan cover Use painters tape (or similar) to secure the magnets in place Install the flange back into your van. Now the vent cover will snap into place when needed.