This is a genuine Poulan replacement part, it is sold individually.
A spark plug is used to deliver electric current from an ignition system to an internal combustion engine.

After time spark plugs will become dirty or fouled.
It is a good idea to replace the spark plug once this happens.
You should gap your spark plug according to the owners manual of the outdoor product you have.

Genuine Husqvarna replacement part, this item is sold individually.
This part is used on all of the Husqvarna Chainsaws listed below.
The purpose of this nut is to attach the Clutch Cover along with the Chainsaw bar.

This is a genuine manufacturer approved replacement part designed for use with chainsaws. It is used to secure starter housing to the unit. This is a metal phillips head screw which is sold individually.

Genuine Husqvarna replacement part, this part is sold individually.
The 503939601 Air Purge does just what the part name says.
It purges the air out of the carburetor.
Then it forces fuel from the fuel tank and fuel line in to the carburetor.

Genuine Husqvarna replacement part, this item is sold individually.
The purpose of the Fuel Tank Bushing is to create a seal and prevent leaks from the fuel tank. The fuel line are inserted in to the Bushing.
It is then pressed into the holes provided in the fuel tank.