Manley Alcohol Fuel Classes ProMod NexTek Series High Performance Valve Springs Leopard Seals Antarctic and Southern Ocean Coalition. From drag strips to short track and endurance circuits, the Manley NexTek series is engineered for serious racers. NexTek springs resist pressure loss and valve train degradation even in the most demanding race conditions. That means more consistent spring force deep into a run, reduced valve bounce, and improved overall stability for high RPM performance. Built to outperform and outlast in real world competition. Extensively tested on the Spintron, dyno and race track (including blown nitro engines) and proven highly effective Higher natural frequency and lower active mass provides improved valvetrain control and higher RPM potential Dual spring design reduces friction, which generates less heat and translates into greatly reduced load loss Smaller diameter, lightweight dual design allows engine to rev higher with improved valve train control Accepts smaller, lighter retainers which also promotes higher revs Ultra clean, high tensile strength chrome silicon material