https://www.gobilda.com/proton-servo-steel-gears-180-rotation-torque-ratio/

The goBILDA® Proton Servo is a standard size servo offering essential servo function on a budget. There are two versions of the Proton: ‘Torque’ and ‘Speed’. Though their gear ratios differ, they are identical in every other way. The ‘Torque’ version sacrifices speed to optimize its performance in higher torque applications. 

While makers of all levels can appreciate the steel gears that form the Proton’s core, the nucleus of the design is beginner-friendly accessibility! That’s why the Proton’s set of features has been pared-down to the bare essentials:

• 180° of rotation to turn your ideas into reality

• 75 oz-in of torque to push your project into innovation

• an H25T spline, which you can use to mount all kinds of rotating components found throughout the goBILDA® ecosystem and the wider hobby market