Deck and screws
The deck is made from wood. There are (were) replacement decks made from metal for sale on Ebay, but they were several times heavier than the wood decks.
The screw size is a metric 5 or just 5m. It is worthwhile to buy a set with a longer thread to allow adhesive rubber foam under the wooden deck to make the ride a bit smoother. They can be purchased at Home Depot. They are probably also available at Lowes also or any other hardware store. The screw head was a little bit smaller but still flat and fit pretty well.