Three Boxes in One. One-piece polymer construction makes the MH Tuff Box leakproof, says the maker - an advantage over conventional sheet-metal diffusers. Installers should appreciate the product's versatility: Each of the available sizes (6x6, 8x8, and 10x10) has a stepped collar that lets it connect to three different diameters of flexible ductwork. Unneeded collars snap off with the twist of a screwdriver. Prices range from $5 to $8. Airtec Products Corp., 800/324-7832,

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