Frequency Sensing Technology (FST) allows the shocks to sense frequency of a bump and automatically adjust damping for superior ride quality, Adjust spring pre-load by hand, no special tool needed, Progressive Rate Main springs specifically designed for touring, 944 FST Ultra Touring shocks are available in three configurations: Standard (Up to 250 lb), Heavy-Duty (250 to 350 lb) and Super Heavy Duty (350+ lb), Made in the USA, Sits 1* lower on most models., Before purchasing or attempting to install shocks that are different than the OEM length, confirm that your wheel travel can be altered without causing clearance issues, such as swingarm/axle to exhaust contact as well as chain/belt guard or tire contact.