The Size 11 double stack by Haydon Kerk Motion Solutions is a 28mm stepper motor linear actuator. Size 11, 28000 double stack series linear actuators are available in three designs - captive, non-captive and external linear versions. Available in a variety of resolutions, ranging from 0.003175mm to 0.0508mm per step. The size 11 double stack series stepper motor linear actuator delivers force of up to 30 lbs (133N). Typical applications include medical equipment, semiconductor handling, valve control, X-Y tables, hand held instruments, or wherever precise linear motion is required.