Smooth-On URE-FIL™ fillers disperse easily in Smooth-On materials. They can be added to materials in different proportions to achieve a variety of working properties and effects. Some fillers are designed for cost-savings, others are designed for specific casting effects or improved physical properties. Other URE-FIL™ fillers are designed specifically for thickening materials for brush-on or trowelable application.

URE-FIL™ 13 is a poly-blend filler used to thicken urethane plastics and epoxies for vertical surface application. URE-FIL™ 13 is added in small amounts for thickening, which allows for additional strength in cured plastic pieces. Flexible urethane mixed with URE-FIL™ 13 can produce a carveable and stampable finish, useful for zoological and theming applications. For example, Simpact™ 80A combined with URE-FIL™ 13 is often used for vine-making applications.