Champion spark plug (RCJ6Y). The spark plug ignites the fuel and air mixture in the engine's cylinder to power the engine. If the spark plug is has fouled (if the tip of the spark plug is burnt or damaged), the engine may not start or may run rough.
Small engine primer bulb. The primer bulb draws additional fuel into the carburetor to help start the engine.
Air filter. If the air filter is clogged or dirty, the engine may not start or may run rough.
Homelite compression spring. Pushes bump knob back out after string is released.
String trimmer fuel tank kit. If the fuel tank is leaking then the tank may be damaged and will need to be replaced.