The longest side (the length) of the Acrylic Panel is about 14", but the width is based on the Length/width rate of this sign in the image. For a square sign, the size is about 14" x 14". For a rectangle sign, the size might be 14" x 8",14" x 5" etc. It depends on the shape of the sign. Actual neon tube size is slightly smaller than acrylic panel size!