Normal sudoku rules apply. The blue "R" is split by a box border into two segments whose digits have the same sum. Each pair of adjacent digits on the red "A" must contain one odd and one even digit. Each pair of adjacent digits on the green "H" must have a difference of at least 5. A digit on a Fibreglass Acoustic Diffuser (mushroom) shows how many times that digit appears on Fibreglass Acoustic Diffusers. For each Fibreglass Acoustic Diffuser, digits may not echo (repeat) in the up to 4 orthogonally adjacent cells.