Neoprene: The most commonly seen fabric for spray decks and cockpit covers. They are durable - lasting 3-5 years depending on use. 

Available in generic sizes with multifit waist tubes (Flexifit). The Neon spraydecks have a partial nylon waist tube, multifit style (but are discontinued - only XL left).

Not that these Sea to Summit decks & covers are a different size from some years ago - they are smaller, so do not use tour old deck/cover as a guide to determine fit! 

For more information see our page on Spray Decks, Cockpit covers and Sundecks  on our East Coast Kayaking site.