This is a genuine Murray replacement part, it is sold individually. It is commonly used in lawn tractors, and is used in various places in the compatible models listed below. It is self tapping, with a 9/16 hex head. Made of metal.

This is a genuine Murray replacement blade, it is sold individually.
It is used on the Mowers listed below.

It is a (3N1) Blade, that can be used for bagging, side discharge and mulching the lawn clippings. 42 inches is a reference to the cut, as there are two blades attached to the deck of the tractor.

This is an OEM replacement part and is sold individually.
Its purpose is to filter out dust and debris from contaminating the carburetor and engine.

When replacing the filter you can open the package in comes in and put a bit of two cycle oil in the bag and let it absorb into the filter. Then remove it from the bag and squeeze it with a paper towel to remove the excess oil.
This will aid the filter in filtering out the unwantables.

The primer hose is inserted into the fuel tank then connected to the Primer.
By pressing on the primmer a few times this assembly fills the carburetor with fuel.
When the carburetor has enough fuel in it, the excess fuel is forced back into the the tank through the fuel return line.

After time the primer hose will become brittle and crack and have to be replaced.
The primer will also lose its elasticity, and may also crack and not be able to suck up the fuel into the carburetor.
And will have to be replaced.

This is an OEM replacement part and is sold individually.
Its propose is to deliver an electric current from an ignition system to the combustion chamber of a gas fueled engine.
It will ignite the air fuel mixture by the spark.
Spark Plugs will usually have to gapped to the manufactures specifications found in the owners manual.

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 better to replace a fouled spark plug, rather then trying to clean it.