It has two bladders (dual diaphragm) giving it much greater stopping power than the smaller single units. A 8" Dual booster gives you 27% more stopping power than a 8" single, making it perfect for larger cars.
BLACK 8" Dual Diaphragm Power Brake Booster universal street rod gm chevy
1968-76 Corvette Power Brake Bendix Booster Brand New Black 8" Dual Diaphragm
1959 1966 Cadillac Black Power Brake Booster 8" Dual Diaphragm
OER PB1083B Universal 8" Dual Diaphragm Power Brake Booster - Black
Universal 8"Dual Diaphragm Zinc Power Brake Booster fits Chevy fitsd Street Rod
GM/ Chevy 8" Dual Diaphragm Power Brake Booster Chrome B10604C