This is a genuine Hitachi replacement part, it is sold individually. Its purpose is to create a seal and prevent air leaks. Over time this gasket will deteriorate and will have to be replaced. This specific gasket is commonly used in nailers, and is compatible with the models listed below.

Genuine Hitachi replacement part, this item is sold individually.
This O-Ring is place in the groove in the piston in all the tool models listed below.
Its purpose is to create a seal in the cylinder, so when the trigger of the tool is activated, will push the driver and piston assembly down and sink the fastener that is being used.
Some of the tools listed offer an O-ring kit that would have all the essential O-rings in it.

This is a genuine Hitachi replacement part, it is sold individually.
The Nose Cap is attached to end of the 884-324 Pushing Lever to prevent the material that it is being used on from getting marred or dented by the pushing lever.

It is a advisable to have one or two extra Nose Caps on hand as they do have a tendency to crack and deteriorate over time. And get lost.

Genuine Hitachi replacement part, this item is sold individually. The purpose of the 877-761 Feeder Spring is to return the feeder to its original position once a fastener has been shot. This part is made of metal and is compatible with the nailers listed below. For install: remove the retaining ring from the feeder shaft. Slide the feeder with feeder spring off of the shaft. The old spring can now be removed and the new one set in place. Slide the feeder with spring back onto the feeder shaft and secure with the retaining ring.

Genuine Hitachi replacement part, This item is sold individually.
The shaft ring is used in the models below to secure various pins and shafts in place.
This is a part made of rubber so it will have a tendency to wear and deteriorate.
It may be a good idea to have an extra one or two on hand.

Genuine Hitachi replacement part, this item is sold individually. The Feeder Spring returns the feeder to its original position once a fastener has been shot. This part is made of metal and is compatible with the nailers listed below. For install: remove the retaining ring from the feeder shaft. Slide the feeder with feeder spring off of the shaft. The old spring can now be removed and the new one set in place. Slide the feeder with spring back onto the feeder shaft and secure with the retaining ring.