api5000API flanges standard is American petroleum institute. API 6a6b6bx flanges dimensions are desned to handle hher rated pressure. We are an API 6a flanges manufacturer. Visit now!API 6B API 5000 (Class 1500) 1-1316″ to 26-34 Pressure Class API 2000 (Class 600) API 3000 (Class 900) s Material Class BB Raised Faced& CC DD & EE Bolts Holes 4 to 48 Face Ring