The difference between SMC and BMC is the length of glass only.Different length of glass results in different mechanical character.

Sheet Molding Compound (SMC) is a compression molding compound often used for larger parts where higher mechanical strength is needed. SMC is a fiber reinforced thermoset material. Glass reinforcement is between 10% and 60%, and glass length is slightly longer than Bulk Molding Compound (BMC) - between 1/2-inch and 1-inch (25mm).

Sheet molding compounds can be molded into complex shapes. Superior mechanical properties and surface appearance, plus excellent electrical insulation make this thermoset material ideal for automotive Class A body panels, high-strength electrical parts, business equipment cabinets, personal watercraft, and various structural components.

Bulk Molding Compound (BMC) is a thermoset plastic resin blend of various inert fillers, fiber reinforcement, catalysts, stabilizers, and pigments that form a viscous. Bulk Molding Compound (BMC) is highly filled and reinforced with short fibers. Glass reinforcement represents between 10% and 30%, with glass length typically between 1/32-inch and 1/2-inch (12.5mm). Depending on the end-use application, bulk molding compounds are formulated to achieve close dimensional control, flame and track resistance, electrical insulation, corrosion and stain resistance, superior mechanical properties, low shrink, and color stability. Its excellent flow characteristics, dielectric properties, and flame resistance make this thermoset material well-suited to a wide variety of applications requiring precision in detail and dimensions as well as high performance.