EX Gear oversized actuators for Sanwa Denshi and Hori Hayabusa joysticks are here.  

The purpose of an actuator is simply to activate the switches either faster or slower depending on the size of the actuator.  The larger the actuator, the less throw and actuation distance, therefore a faster and more precise inputs

The stock Sanwa Denshi actuator measures 10.7mm.   Available EX Gear sizes, 11.5, 12, 12.5 and 13mm.  These also are compatible with Hori Hayabusa joysticks