I sell reusable air duct covers.  They're used to seal air vents, registers, or whatever you call them.  Unlike some other products that cover air vents to block drafts, Vent Caps are rugged tools used to seal air vents for Duct Leakage Testing, the diagnostic testing of a home's ducted a/c system.  My reusable register covers can cut your DuctBlaster® setup time in half, help you spend less time with/on/carrying a ladder, and save you tons of money on disposable plastic tapes.  Grill masks, register sealing films, duct masks, and even plastic wraps all have to be ordered OVER AND OVER again.  Vent Caps are 100% resuable and extremely long lasting they are. (Check out the Testimonials Page)  In other words, once you've bought them, you don't have to buy anything else.  Conversely, you'll have to buy "nothing", which of course, I am more than happy to sell you!  ;-)