This set of 4 magnetic vent covers will help your furnace or air conditioner use less energy! Help your heating or cooling system work more efficiently! In summer, cover the floor level return air register with a magnetic sheet so only warmer, ceiling level air is returned. In winter, use a magnetic vent cover over the ceiling level return air register so only the lower, cooler air is returned to the furnace. For additional savings on heating and cooling costs, use these thick magnetic vent covers to close off registers without dampers in unoccupied rooms. Not only will you save energy, but you'll be more comfortable since the heat or air conditioning will be directed to where it's really needed. Each 8" x 15-1/2" magnetic register cover can be cut to fit with a scissors, and you can paint them to match your decor. 0.025" thick. You get 4 white magnetic sheets per set!