I bought some Fusi-boo on sale at Joanns and it was very thin, in fact too thin. I did like the fusible quality though -- it was very fast to sandwich (I was doing a QAYG) & quilt. I had a cotton pieced front and back, and used the Fusiboo for batting. The quilt turned out fine except it is much thinner than I expected and certainly not as warm as cotton. So I can say for sure that Fusiboo will be very thin and lightweight if that's what you're looking for.