This Spectre Air Intake Plenum has a single inlet with a 4 inch outside diameter. Manufactured from polished cast aluminum, this plenum is designed to be compatible with Spectre 4 inch tubing, filters, and accessories. 3-1/2 inches tall and measuring 9 inches from air cleaner stud to the inlet, it fits carburetors and TBI throttle bodies with a 5-1/8 inch inlet. All of our air intake components are designed and built using high quality materials and engineered for optimum fit and function.