This very thin Razor Foam is commonly used for small midge and mayfly patterns.  Razor Foam is also used on many of today's larger foam hopper and stonefly patterns on topo of a the wing or on top of other layers of foam to add visibility to the fly.  Razor foam is becoming much more popular and is being incorporated into more fly patterns than ever before. 

Each package of Razor Foam comes with four 4.5" x 1.75" pieces.  Two of the sheets are 1mm thick and the other two sheets are 0.5mm thick.