PS, 490 Sport Series shock set. 13.5". STD Duty. Black 91-05 Dyna

490 series - Sport Series. A true sport performance shock, with a competitive price tag. Features a high pressure nitrogen monotube with deflective disc technology and a linear rate spring for the most consistent feel throughout the damper stroke on both street and track. Preload and rebound adjustability by hand. An engineered jounce bumper with a built-in metal cup smooths and controls bottoming out. What are Progressive Suspension's 'STD Duty' vs '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.