All rotary engines (including RX7, RX8, etc.) require additional parts (counterweights) for proper function.
The Streetlite flywheel is considerably lighter than stock and is the most durable flywheel offering from ACT. Materials are properly distributed for maximum strength, lower inertia, good heat tolerance and rigidity. ACT's Streetlite flywheels are preferred for street or drag racing. ACT flywheels are serviceable and can be resurfaced with no need to purchase additional parts.