You can choose the version with servo or without
The difference between CM-785HB and CM-700 is that the first code include the servo, the second one is just the gearbox
If you want to buy the servo HS-785HB you can find it here.
The CM-700 Servo Gearbox is designed around the popular Hitec HS-785HB sail winch servo (not included) to create a high-torque Servo Gearbox. The stock Hitec servo can rotate several turns in factory form (approximately 4 turns on most Tx/Rx systems; up to 8 turns with a 650-2350usec signal). When an HS-785HB servo is installed into the gearbox, the total amount of rotation is decreased by the ratio selected but the torque and precision is increased by the ratio. The lower the gear ratio, the more precision and torque it will provide but the speed and amount of rotation will be decreased. By incorporating threaded side mounts you can now easily attach these servo gearboxes to numerous ServoCity products including tubing and channel; making it easier than ever to incorporate a servo gearbox into a custom pan & tilt, mechanical device, or robotic structure. Five different gear ratios are available in order to find the right balance between torque and rotation. Positioning feedback remains since the servo is completely stock and unmodified in any way. The CM-700HB can handle tremendous side loads with the dual ABEC-5 precision ball bearings which support the hardened 1/2” stainless steel hollow shaft. The shaft is hollow with a .382” inner diameter to allow wires from cameras, sensors or other devices to not tangle during multi-turn movements. The brass pinion gear meshes to a high-grade 7075 aluminum 32 pitch hub gear which is fastened to the output shaft of the gearbox with a 1/2” clamping hub. The .770” clamping hub has 6-32 tapped holes which allow easy attachment of various components.