This is the Malossi Racing torque driver spring. This is 60% stiffer than your stock spring.

Upgrading your torque driver spring helps improve acceleration, and hill climbing performance. These Malossi Springs are Silicon-steel springs with high carbon content, heat-treated, dynamically balanced, kiln painted and designed and calculated for each specific application.

Malossi Springs can be divided into three categories:
REINFORCED SPRINGS with high stiffness
SUPER REINFORCES SPRINGS with exceptionally-high stiffness
RACING SPRINGS designed for high performance use and competition machines

This torque spring fits on the following scooters:
APRILIA
MOJITO 50 2t CUSTOM, SCARABEO 50 2t STREET (PIAGGIO), SCARABEO 50 4t (PIAGGIO C373M), SPORTCITY ONE (PIAGGIO C377M) 50 4t, SPORTCITY ONE STREET 2T euro 2 - 50 2t, SR 50 2t LC 2004-carb (PIAGGIO), SR 50 2t LC R-carb (PIAGGIO)

DERBI
ATLANTIS 50 2t BULLET, GP1 50 2t LC, GP1 50 2t LC OPEN, GP1 50 2t LC REVOLUTION

GILERA
DNA 50 2t LC, EASY MOVING 50 2t, ICE 50 2t, RUNNER 50 2t LC, RUNNER 50 2t LC PureJet <-- 2005, RUNNER 50 2t LC PureJet 2006 -->, RUNNER 50 2t LC SP <-- 2005, RUNNER 50 2t LC SP-carb (C451M) 2006 -->, STALKER 50 2t, STORM 50 2t, TYPHOON 50 2t, TYPHOON X 50 2t

ITALJET
JET SET 50 2t, TORPEDO 50 4t

KYMCO
DINK 50 2t, K 12 50 2t, PEOPLE 50 2t, SUPER 9 50 2t LC, TOP BOY - COBRA 50 2t

PIAGGIO
DIESIS 50 2t, FLY 50 2t, FLY 50 4t, FREE 50 2t, LIBERTY 50 2t, LIBERTY 50 4t, TYPHOON 50 2t 2007 -->, VESPA ET2 50 2t [carb.], VESPA ET2 50 2t 2000, VESPA ET4 50 4t, VESPA LX 50 2t, VESPA LX 50 4t, VESPA S (C381M) euro 2 - 50 2t, VESPA S 4V (C386M) euro 2 50 4t, ZIP 50 2t 2000, ZIP 50 2t FAST RIDER, ZIP 50 2t LC SP <-- 2000, ZIP 50 2t LC SP 2001 -->, ZIP 50 4t

YAMAHA
BW'S - BW'S NG 50 2t (A137E) euro 2