This is an OEM replacement part,it is sold individually.
The Bumper Head Knob is the part of the trimmer that when struck on the ground, advances the trimmer line in the spool.

To remove the Bumper Head Knob, thread it off the spindle of the gear box assembly.

This is a genuine OEM replacement part, it is sold individually.
The propose of the Reel and Line Assembly is to dispense the cutting line for the trimmer models below.
This is a dual line trimmer.
The diameter of the line used in this reel is 0.080

This is an authentic manufacturer sourced replacement cotter pin. It is a standard hardware commonly used on a variety of Craftsman lawn and garden equipment. Depending on the model of your equipment it will be used in different locations to secure two parts together. Please make sure to check appropriate diagrams for correct application for this part. This metal cotter pin is sold individually. It is best to use pliers to remove or install this part.

A carburetor basically consists of an open pipe through which the air passes into the inlet manifold of the engine.
The pipe is in the form of a Venturi: it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part.
Below the Venturi is a butterfly valve called the throttle valve — a rotating disc that can be turned end-on to the airflow, so as to hardly restrict the flow at all, or can be rotated so that it (almost) completely blocks the flow of air.
This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints.

Fuel is introduced into the air stream through small holes at the narrowest part of the Venturi and at other places where pressure will be lowered when not running on full throttle.

This OEM fuel tank assembly is made out of Plastic and it includes the fuel lines, fuel cap, and fuel filter. It is a common part in gas trimmers that is used to hold the fuel needed for the engine. It is very important to replace the fuel tank if it is cracked or damaged to avoid further damage or serious injuries. Make sure to drain the gas tank before starting a repair.

This is a genuine OEM replacement part, it is sold individually.
This is the front wheel on the models shown below.
There are two of them on each mower.
The wheel has a ring gear on the inside which is driven by the Right hand and Left hand smaller gear that attaches to the front axle on the transmission assembly.