GC Labels' Combustible 4x4 purple labels are used as a cautionary label.   These labels are for use on packages of less than 119 gallons and a flash point of of 100 degrees.  These are for discretionary use only, and are not required by DOT.  These purple labels are printed on heavy-weight paper, printed with fade resistant pigments and our adhesives are formulated for permanent adhesion in various climates, environments and surfaces. Once affixed, these labels will not come off.