422 series - Better. Two inches; standard to 2" lower; of ride height adjustment and adjustable preload. High pressure gas system in a dual coil shock system. The shocks include a new fill valve to replace the stock one. Also available in the RAP (Remote Adjustable Preload) series; which comes with the added convenience of a Remote Adjustable Preload; located behind the left passenger peg; for easier accessible adjustments. What are Progressive Suspension''s ''Heavy Duty'' shocks? If you are a lightweight rider with a lightweight passenger; STD Duty is probably your best choice; heavy duty shocks will give you a harsh ride. For Big Guys & Gals with a lot of baggage; Heavy Duty springs are the way to go. Heavy Duty is not better; it''s different.Heavy Duty shocks or springs are recommended to be used on motorcycles that are operated at or near the manufacturers maximum load rating over 50% of the time.

Specifically designed for the 12-16 Dyna FLD Switchback. The coil spring is slightly heavier & lower coil cover is styled differently to allow better adjustment with saddlebags installed. 412 series shocks: Best value Progressive Suspension shock; great as stock replacement. Nitrogen charged double steel wall body. Multi-staged velocity sensitive valving. Five position cam style preload adjustment. Note: Black 412 shocks may be supplied without lower cover. What are Progressive Suspension''s ''Heavy Duty'' shocks? If you are a lightweight rider with a lightweight passenger; STD Duty is probably your best choice; heavy duty shocks will give you a harsh ride. For Big Guys & Gals with a lot of baggage; Heavy Duty springs are the way to go. Heavy Duty is not better; it''s different.Heavy Duty shocks or springs are recommended to be used on motorcycles that are operated at or near the manufacturers maximum load rating over 50% of the time.