After more than a decade of ruling the roads with Progressive's road proven 440 Series shocks, We’ve unveiled another breakthrough design. Dubbed Frequency Sensing Technology (FST) for its unique ability to dynamically adjust damping as you ride. The result is superior performance no matter the road conditions. A top mount threaded preload adjuster allows for fine tuning with a simple twist of the cap. 

• Frequency Sensing Technology (FST) Allows the shocks to sense the frequency of a bump and automatically adjust damping for superior ride quality
• Deflective disc valving
• Adjust spring pre-load by hand,no special tool needed
• Progressive rate spring 
• Lifetime Limited Warranty
• Made in USA