I've used celing tiles before too. The ones they are talking about are the type that are used on schools and office buildings. They are probably 1.5'x4' so they are big enough for most 40 and 60 sized projects. I switched to pink home insulation. I find that the big T-pins hold great in it and you can get them BIG. The sheets usually run 4'x8' and you just cut the size you need. Best thing of all is the foam holds together if it's nicked and doesn't create any dust like my celing tile did.