This is a very small light sensor. A photo resistor (also known as a photodector, or photocell) changes resistance depending on the amount of light it is exposed to.
The Micro Maestro is the smallest of Pololu’s second-generation USB servo controllers. The Maestros are available in four sizes and can be purchased fully assembled or as partial kits.
This is the chain and sprocket kit for the IG52-DB4 robot platform. It includes 10 tooth and 15 tooth sprockets, 5 feet of #25 chain, and 4 connecting links.