This is an OEM replacement part and is sold individually.

The purpose of this spark plug is to deliver an electric current from an ignition system to the combustion chamber of a gas fueled engine, igniting the air fuel mixture by the spark.

Over time a Spark Plug will become fouled because the air/fuel ratio may be set wrong, worn piston rings, carbon build up, and other factors.
It is best to replace a dirty spark plug, rather than trying to clean it.

It is important to gap your spark plug according to the owners manual of your product.

This is a genuine OEM replacement part. This part is made out of plastic. The ratchet pawl is necessary to engage the recoil starting system to the engine. If the pawl is worn the recoil can slip and make it difficult to start the engine.

This is a genuine OEM replacement part, it is sold individually.
The purpose of this filter is to help eliminate dirt, dust and debris from contaminating the carburetor and damaging the engine.
A dirty air filter can cause the engine from operating properly.
This filter can be cleaned a time or two by using an air supply. But it is advised to replace it once it becomes dirty.