Material: aluminum alloys, titanium and special steel Primary spring: 6 original Ducati helicoidal springs (not included) Secondary spring: spider spring code 001MG017 Basket: Original or STM 48/12 Tooth (ADU-0010, ADU-0020) Features: slipper system SS1 ? device to control the opening - progressive engagement plate - clutch pack inspection system (CPI) Compatible disc pack: Original or STM 48 Tooth Plates (ADU-0030, ADU-0040) Tools: hub-drum mounting tool code UTL-0020(recommended) The Original Slipper Clutch is our most economical clutch. This clutch retains the classic 6 helicoil primary spring configuration found in stock Ducati dry clutches. However, it offers great STM technological features like 'Ball & Ramp' actuation for smooth slipper clutch operation, the STM exclusive 'PEP' - Progressive Engagement Plate to decrease the abruptness during closing of the clutch, and now comes with an 85mm Diaphragm Secondary Spring for increased tune-ability. The secondary spring is what controls the amount of engine brake. The lighter the secondary spring, the less engine brake; the heavier the secondary spring, the more engine brake. The 85mm diaphragm secondary springs are weighted in Kilograms and offered in 10Kg increments. There are 6 different weights to choose from (sold individually). Through the use of varying