This is a set screw lock collar. It is for a 0.438 or 7/16 inch shaft. They are steel and zinc coated. Perfect for keeping your shafts or bearings in place.
Shaft Collars (sometimes called lock collars) are easy to install; the collar provides an easy way to keep your shaft from sliding or your flanged bearing from coming out.
Ultrasonic Module HC-SR04 Distance Measuring Transducer Sensor.
This is a prebuilt MLT-JR tracked robot platform equipped with 12V 32-millimeter motors, a motor controller and an authentic Arduino for autonomous control.