There are a multitude of combinations when it comes to selecting a Flywheel Cage and Flywheels which can be quite confusing to many.  Dart velocity (fps) primarily is a result of flywheel gap distance (crush), supported secondarily by appropriately sized motors, wiring, switch, battery pack and other system components.  This flywheel gap is the measured distance between both flywheels and is a combination of Flywheel Cage Size and Flywheel Root Diameter.

To calculate the flywheel gap/distance, it is simply:

Flywheel Cage Size (distance between motor shaft to motor shaft) 
minus
Flywheel diameter (root diameter)

Example:
Worker Black 42.5mm metal cage has a motor shaft to shaft distance of 42.5mm
Worker Black Smooth Flywheels have a root diameter of 34.5mm
42.5mm - 34.5mm = Flywheel gap of 8mm (look up table: 8mm has an expected fps of 140-150fps)

Look up table
Flywheel Gap / Expected FPS
10mm / 100-110fps
9.5mm / 110-120fps
9mm / 120-130fps
8.5mm / 130-140fps
8mm / 140-150fps
7.5mm / 150-160fps
7mm / 160-170fps

Please note: This is to be used as a expected guide only.  There are many variables which will slightly vary the outcome: flywheel (surface type, concavity), dart type (quality old and new), motors used, envorimental conditions, electrical components used, quality of work (soldering etc), flywheel cage material (plastic cages flex more than metal).  Upgrade motors MUST be used: smaller the gap, the more load on the system and need for a higher torque motor.  Rewire with appropriate gauge wire and switch (mosfet if needed) must be performed with use of a proper Lipo pack.  Also remember: Smaller the gap, more dart velocity, but also more wear and tear on darts.  Any questions on setups, please email or message us.