With spherical style bearings. 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.