• 2 FMI billet aluminum rear lower trailing arms
• Ultra-Flex joints — 17-4 stainless steel center ball in a serviceable urethane body
• External grease zerk at each joint, low profile so it stays accessible with the arm on the truck
• Spacers and installation hardware

The Ultra-Flex center ball is machined to the application, so no additional spacers are needed beyond what ships in the box.

The Gen 3 Raptor runs a five-link rear axle. The lower links take the fore-and-aft load — everything the engine puts down and everything the brakes take back goes through them. The uppers control axle wrap and pinion angle, and the panhard bar handles side to side.

Every one of those connections is a rubber bushing from the factory. Rubber is chosen for isolation, not for location. Put real load through it and it compresses, the axle moves relative to where the chassis thinks it is, and the rear end feels disconnected under power — the same compliance that turns into wheel hop on a hard launch.

Billet arms on spherical joints replace that with a defined pivot. Of the two arm sets, the lowers are the ones most owners notice first.

Our patent-pending joint, and the reason to choose this version over the uniball arms.

How it is built

A 17-4 stainless steel center ball pressed into a urethane body, which is pressed into a laser-cut stainless steel outer sleeve closed by two stainless side caps. The cartridge presses into the arm and is retained with a circlip. The grease zerk threads into a slotted hole in the sleeve, so the sleeve cannot rotate in the arm.

Why it matters

• Greaseable on the truck through the external zerk — no removing the arm to service the joint.
• Quiet. The urethane damps impact and isolates road noise instead of squeaking and clunking the way a worn uniball does.
• Corrosion resistant. Stainless internals that stay constantly lubricated — what you want in wet, humid or salted conditions.
• Rebuildable for the cost of a urethane body, not a complete joint assembly.
• Protects the arm. The stainless sleeve means urethane never works directly against your billet aluminum, so the bore stays true.

Read the full Ultra-Flex joint breakdown →

We build the Gen 3 billet rear arms two ways. Both are billet aluminum, both bolt into the factory mounts, both give the same 15 inches of rear wheel travel. The joint is the only difference.

Ultra-Flex — this kit. Greaseable in place, quieter as it wears, rebuildable with a urethane body, better in wet or salted conditions. The choice for a truck that still gets daily driven.

Uniball — 1" FK uniballs, tighter and more direct, and the uniball is a replaceable wear item. The choice if you specifically want a uniball and are comfortable pressing a bearing when it wears. See the uniball rear lower arms.

Fits the Gen 3 and Gen 3.5 Ford F-150 Raptor, model years 2021, 2022, 2023, 2024, 2025 and 2026, including the Raptor R.

The Raptor R uses the same rear suspension architecture as the V6 truck, so these fit it unchanged. Stock-length only — this is not a long travel kit and it does not change rear geometry.

Bolt-on. The arms use the factory mount locations and the spacers are machined to suit, so there is no cutting, no welding, no fabrication and no alignment required afterwards.

Support the truck safely and take the load off the rear axle before removing the factory arms. We recommend the work is done by an experienced individual or shop. Guides are at Install Instructions, and we do in-house installation in Mesa.

Four options: raw billet aluminum, black anodized, FOX orange anodized and blue anodized.

Raw is a finish choice, not a lesser part — plenty of builds run raw billet deliberately for the machined-aluminum look. Anodized parts should be cared for as anodized aluminum; see the care notes before you take a pressure washer or a harsh wheel cleaner to them.

Do these fit a 2025 or 2026 Raptor?

Yes. They fit 2021 through 2026 Gen 3 and Gen 3.5 trucks, Raptor R included.

Do the arms include the installation hardware?

Yes. The kit ships as two billet aluminum rear lower arms with spacers and hardware.

Lowers or uppers first?

Lowers. They carry acceleration and braking load, so they are the pair you feel most. The panhard bar comes before either — it is the least expensive part of the rear suspension and makes the biggest immediate difference.

Will these stop wheel hop?

They address its main cause. Wheel hop comes from the rear suspension deflecting and rebounding under load, and rubber bushings in the lower links are where most of that deflection lives. Replacing them with a defined pivot removes the compliance that feeds it.

Can I grease the joint without pulling the arm off?

Yes. The external grease zerk stays accessible with the arm installed on the truck.

Will they make the ride harsh?

No. The urethane body damps impact and isolates road noise rather than transmitting it into the chassis, so you get precise axle location without the harshness that usually comes with metal-on-metal.

What happens when the joint wears?

You replace the urethane body, not the arm and not a complete joint assembly. Service parts are under Serviceable Parts.

Do I need an alignment afterwards?

No. Stock-length arms into factory mounts do not change ride height or rear geometry.

Where are they made?

Designed, machined and finished in-house at our facility in Mesa, Arizona, USA.

• Billet panhard bar with Ultra-Flex joint — the one we would buy first
• Billet rear upper trailing arms — Ultra-Flex, to complete the set
• Rear bump stop kit and rear limit strap kit — the cheapest real gain on the truck
• Rear link frame mount gusset kit — the factory link mounts are the known crack point

Side by side on Gen 3 Rear Links & Panhard Bar, or the full catalog on Gen 3 Raptor Rear Suspension.