This regular size is widely use on most model airplane in the market.
The center hole of the trunion is 4MM
Dimension
Servoless Retractable Landing Gear
After 10 seconds Auto power-off Protection system
Double Shock Absorption Design
Completely protect the gears
Dimension:65.8*35.1*25.1mm 2.59*1.38*1.0inch
Maximum travel: 90°
Torque: 2.5kg-cm
Speed: 0.7s/60°@4.8V 0.55s/60°@6V
Operating Voltage: 4.8v-6v
Weight: 32g
Used for airplanes wing span around 1.5m
Support Flight Weight 3kg
Φ4mm