Fox Racing Shocks 981-40-403-L Factory Race 4.0 x 18 External Bypass 5-Tube Piggyback Shock Left

The Fox Racing Shocks 981-40-403-L is a Factory Race Series 4.0-inch external bypass piggyback shock absorber featuring a 5-tube bypass configuration and 18 inches of travel, sold individually as a left-side unit. Built on over 30 years of race-proven external bypass technology, this shock delivers uncompromising off-road damping performance for serious competition and high-performance trail use.

Fox's externally adjustable, position-sensitive damping architecture uses five bypass tubes to allow oil to flow around the piston at controlled points in the stroke, generating precise damping forces that support the vehicle through every phase of suspension travel. The piggyback reservoir provides additional oil volume and heat dissipation capacity to maintain consistent performance across extended runs.

Key Features:

• 4.0-inch body diameter with impact-extruded and CNC-machined 6061-T6 hard-anodized aluminum construction for corrosion resistance and light weight
• 18 inches of travel — compressed length approximately 28.54 inches, extended length approximately 46.54 inches
• 5-tube external bypass design for externally adjustable, position-sensitive damping tuning
• 17-4 H900 stainless steel piston rod — significantly stronger than standard high-carbon steel rods, providing superior resistance to rock chip damage and rod deflection
• Race-developed high-flow piston for smooth and efficient damping response
• Gen 3 clicker adjusters on 1-inch bypass tubes with 25% increased adjustment range over previous generation; color-coded seals for compression and rebound identification
• Piggyback reservoir with rotatable tube and reservoir positioning to clear obstacles and chassis components
• Redundant sealing pack system — main seal, wiper seal, and scraper seal for leak-free performance in harsh environments
• Black-anodized CNC-machined 6061-T6 billet aluminum components throughout
• FOX Racing proprietary shock oil formulated for extreme off-road performance
• Fully rebuildable and serviceable; custom valving options available
• Sold as a single left-side shock

The Fox Factory Race 4.0 External Bypass shock is the choice of Trophy Truck and desert race competitors worldwide, and brings that same championship-caliber technology to custom off-road builds. Its externally tunable bypass tubes allow precise adjustment for vehicle weight, terrain type, and driving speed without disassembling the shock.