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Front Anti-Roll Bar Bush (Polyurethane) - 21mm - for Porsche 964 Turbo & 993 Carrera. Powerflex Heritage Collection ❭ PFF57-601-21H
- Porsche 964 (911) TURBO 3.3L 1991-93
- Porsche 964 (911) TURBO 3.6L 1991-93
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) C2S 1994-97


Porsche 964 Carrera - With PR 491 (Turbo Look)
Porsche 964 Turbo 1991-94
Porsche 993 Carrera - Excludes C4S & Models With Sports Suspension (PR 030)
Diagram ref. 3.
These bushes are a direct replacement for the following Porsche part numbers: 96434379221
NOTE: Due to the vehicle's age and some ambiguity in the official catalogue, we highly recommend measuring your anti-roll bar before ordering to ensure you select the correct size.
The Powerflex Range:
Road Series (Road & Fast Road) - POWERFLEX Road Series bushes improve your cars’ road holding and chassis performance by controlling the amount of unwanted flex in the suspension. This means the suspension is doing what it is supposed to. It means your tyres have greater contact with the road at all times, therefore, improving safety and performance. Correctly formulated polyurethane is as good if not better at noise, vibration and harshness suppression when compared to worn rubber. Our Road bushes offer Prolonged tyre life, Improved performance, Increase safety, and Greater cost-effectiveness.
Black Series (Track & Motorsport) - POWERFLEX Black Series bushes are manufactured using our Black 95 Shore A compound to provide maximum control of chassis geometry. They are designed for the Track, ready to Race and are engineered to be the best. This compound can be up to 80% more resistant to load than standard rubber and 25% stiffer than our purple performance material. If your requirements are purely for the ultimate in handling and chassis performance then Powerflex Black Series are unique, offering the most precise and accurate alignment for your chassis.
Heritage Collection (Classic & Restoration Use) - POWERFLEX Heritage Collection bushes are manufactured using modern-day materials with properties biased for the road. These dark grey coloured bushes will improve any collector’s car, whilst retaining the same standard appearance of a rubber bush. Our new range speaks to the growing demand for quality replacement parts that have an aesthetic in keeping with’ the look of the original part and restoration project as a whole whilst carrying all of the performance and longevity benefits offered by Powerflex’s unique blend of polyurethane. Going a step further than simply using the same material and durometer of hardness for all of our parts, each part location has its own shore designation to ensure improved suspension performance without discomfort or vibration, all of which ship in our new ‘Classic’ Dark Grey colour suitable for all road-based applications.
Powerflex Materials:
The materials used by Powerflex are colour coded to make them easily identifiable. Below explains the shore rating and their common uses.
Red 65A – Used for our Universal exhaust mounts and diesel engine mounts.
Yellow 70A – Mainly used for engine mounts, diff mounts and subframe mounts or areas where the bush needs a lot of movement and absorption.
Purple 80A – Our most common material. This is used in most areas of the suspension and provides the right mix between performance and compliance.
Black 95A – Our hardest material. This is used mostly for our Black Series range or in our Road Series where the vehicle’s standard suspension demands require us to use this hardness of material i.e. in areas of high load.
Grey* - Used specifically for our Heritage Collection. This can be any of the durometers mentioned but will always be the same as the equivalent part from our Road Series i.e. if it’s Purple 80A in our Road Series, it’d be Grey 80A in our Heritage Collection. On our Road Series and Heritage Collection kits, we can use a mix of all 4 of our materials. During the development stages, we test the original bush and see what the requirements are for strength and movement. At that point, we then decide which of our materials would be best suited. We don’t believe in a one material suits all rule. Manufacturers will do the same and will use different shore rubbers, however, it’s not as noticeable as all rubber bushes look visually similar.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
PFF57-601-21H
The product you are viewing cross references to these numbers

Anti-Roll Bars (ARB’s) play an important role in a vehicle’s suspension system, helping to reduce body roll by transferring cornering load from one side of a vehicle to the other.
Often mounted to the vehicle’s chassis with rubber bushes, these bushes ensure the bar works as intended. To prevent the anti-roll bar from moving laterally within its mounts when turning, OE manufacturers will either bond the bushes to the bar, add dead-stops to the bar itself, or rely solely on the clamping pressure of the rubber.
But what happens when those bushes wear and need to be replaced? Often anti-roll bars with bonded bushes come as a costly complete assembly, so the alternative is to fit a more cost-effective unbonded polyurethane replacement, like the many we offer.
In most cases, friction from the bush will prevent any side-to-side bar movement. Still, when turning aggressively or cornering at higher speeds, a laterally shifting anti-roll bar decreases the efficiency and effectiveness of the bar, changing the dynamics of your suspension system in unpredictable ways. It also poses the risk of the bar fouling on other areas of the vehicle or suspension system.
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