Oftentimes the designer says to use "film type" or "fabric type" water soluble stabilizer. If they recommend one or the other, you would use Sulky Ultra Solvy
(one layer) for the film type. If they use the other than you would use Sulky Fabri-Solvy
(2 layers). If they don't tell me, I use 2 layers of Fabri-Solvy. Very rarely would they say to use 2 layers of the film type - Ultra Solvy.