The Mack Replacement Pipe is a practical and durable solution for replacing the 4ME-21783P4 OEM part. With a 4" diameter and aluminized construction, this pipe fits most MR Mack makes and models, making it a versatile and cost-effective option for truck owners. Sold individually, this replacement pipe offers a straightforward and efficient solution for maintaining and repairing Mack trucks, ensuring optimal performance and longevity.