KYB 5640021 MonoMax Heavy-Duty Monotube Gas Strut

The KYB MonoMax 5640021 is a heavy-duty monotube gas strut engineered for trucks, SUVs, and 4x4s that face demanding real-world conditions. Built on KYB's top-tier MonoMax platform, this strut delivers the highest level of handling, control, and durability in the KYB lineup — purpose-built for vehicles that tow, haul, plow, or go off-road.

The large-bore monotube design outperforms conventional twin-tube struts by providing superior damping response and fade-free performance that automatically adapts to changing driving conditions. Whether navigating rough terrain or managing heavy payloads on the highway, the MonoMax maintains consistent control throughout the entire stroke.

Key Features:

• Heavy-duty monotube construction — delivers maximum damping force and heat dissipation for sustained performance
• Large bore design — provides additional stability for high center-of-gravity and heavily loaded vehicles
• Zinc-coated steel piston ring — work-ready durability designed to resist corrosion and wear
• Fade-free performance — automatically adjusts to driving conditions without loss of control or handling
• Includes off-road dust boot — protects the strut shaft from dirt and debris in harsh environments
• KYB Lifetime Limited Warranty — covers defects in materials and workmanship for the life of vehicle ownership
• Hardware included — comes with necessary washers, bushings, and nuts; factory mounting bolts are reused

KYB is a globally recognized original equipment supplier, manufacturing aftermarket products using the same materials, facilities, and techniques as OE production. The MonoMax 5640021 is sold as a single strut unit.