This is a brand new 8" ZINC DUAL brake booster.  This 8" booster is ideal for most small to mid size street rods and customs.  The booster mounts with a 4-bolt pattern.  The 4 bolts are in a perfect square and are 3 3/8" apart (center to center). This is a great upgrade from a single diaphragm booster. The 8" dual booster offers 27% better stopping power over 8" single boosters, making this setup much better for increased safety on your vehicle.