This is a genuine Porter Cable replacement part, it is sold individually.
Deteriorated O-rings that cause air leaks, a trigger valve that won’t fire, or a leaking cylinder seal or a Piston Stop, will prevents the gun from making a complete stroke.
You will notice the symptoms of this when the nails are not being driven into the material all the way.
You will need to tear down the nail gun and inspect this part to see if it is broken or has been worn down.

This is a genuine Porter Cable replacement part, it is sold individually.
The purpose of the 890725 Retainer is to secure the pins used on the model numbers shown below.
It is advised to check the condition of the retainer often, for the reason the do deteriorate over time and can fall off of the pin they are retaining.

This is a genuine Porter Cable replacement part,it is sold individually.
The Safety Pad is attached to end of the safety to prevent the material that it is being used on from getting marred or dented by the safety arm.

It is a advisable to have one or two extra pads on hand as they do have a tendency to crack and deteriorate over time.

O-rings are designed to contain thousands of pounds of pressure by creating a seal between two or more parts. O-ring measurements are defined by the inside diameter and the thickness.

There are many causes for O-Ring failure, such as pressure, friction, temperature or chemicals. The most common are:

This is a genuine Porter Cable replacement part, it is sold individually.
The No-Mar Pad is attached to end of the safety to prevent the material that it is being used on from getting marred or dented by the safety arm.

It is a advisable to have one or two extra pads on hand as they do have a tendency to crack and deteriorate over time.

Genuine OEM replacement part, this item is sold individually.
This part acts as a piston bumper.
After the Air Tool is fired the piston will rise up through the cylinder and strike this part.
As the piston is rising it will also expel the exhaust through this part