The piece is red 2.5" X 2.5" square, Lattice design with 2 studs by 2 studs solid tile in middle and 8 studs on each outside around the edge
1 Answer
It's 4151 Plate, Modified 8 x 8 with Grille. There's a newer variant with a hole, too.
In red, it was in only one set: 6989 Mega Core Magnetizer