The double deflection supply grille shall be a Krueger
model 880 (steel) or 5880 (aluminum). This grille must have
individually adjustable blades on 3/4 centers with friction
pivots (plastic blade pivots are not acceptable) made of 22
gage steel (880) or 0.025 aluminum (5880). The frame of
the grille must be constructed of 22 gage steel (880) or roll
formed aluminum with minimum 0.032 thickness (5880) for
sizes less than and equal to 24x24 and extruded aluminum
with nominal thickness 0.040 0.050 for sizes greater that
24x24 with countersunk screw holes. This frame must also
produce a border of 1 1/4 around all sides of the grille with
mitered corners.
