Specifications include, but are not limited to: 1. Frames. Frames should be constructed of 24 gauge galvanized steel. Downstream support for media should be provided by number 10 metal lathe. Frames should be fabricated to fit the unit opening in combination of industry standard sizes where possible. Blank sections should be limited to 2" maximum width unless larger sections were installed by the unit manufacturer as original equipment. Certain classes of smaller units will require nominal 1" frames of nonstandard sizes. All air handlers which will accept 2" frames should be fitted with filter frames of maximum thickness. Successful bidder shall furnish all filter frames. 2. 1/2" media. Media for nominal 1" frames should be non-woven 1/2" thick, 100% polyester fibers, bonded together with a fire retardant resin. Initial Resistance at 300 fpm will be .012" W.C.; final resistance shall be 1.00" W.C.; atmospheric efficiency<20%; weight arrestance 85%;dust holding capacity 220 grams. Hobbs Model HP50D or equal. Use of the Hobbs brand name and Model is for the purpose of describing the standard of quality, performance, and characteristics desired and is not intended to limit or restrict competition.